◄UNIT 1: BASIC BIOCHEMISTRY OF LIFEUNIT 3: FERTILIZERS ►

UNIT 2: HUMAN REPRODUCTION AND FAMILY PLANNING

  • UNIT 2: HUMAN REPRODUCTION AND FAMILY PLANNING

    Key Unit Competence:
    Explain the role of human reproductive hormones,
    stages of pregnancy and family planning methods.

    Introductory activity 2
    Observe the photo below and answer the questions that follow:


    a) The woman in A is pregnant. What do you think about the origin of the
    fetus in the womb of the pregnant woman?
    b) Use the photo B to imagine the embryonic development in mother’s
    uterus.
    c) Use the photo in B and identify the observable parts of the female
    reproductive system. Are you satisfy with that description? Justify your
    response.
    d) The child on the photo is a boy. Can you identify the parts of the male
    reproductive system? What represent the gesture of that boy? Are
    challenging!!!!
    e) What do you think about foetus position observed in mother’s uterus
    on the photo B?
    f) The child boy on picture A is the first borne of her mother and the
    fetus in the womb will be the second and last borne of this mother.

    Can you advocate for such a family planning? Give reasons

    Animals reproduce sexually, but some, on occasion, can reproduce asexually.
    Sexually reproducing animals have gonads for the production of gametes,
    and many have accessory organs for the storage and passage of gametes
    into or out of the body. Animals have various means of ensuring fertilization of
    gametes and protecting immature stages. Human reproduction is any form of
    sexual reproduction resulting in human fertilization. It typically involves sexual

    intercourse between a man and a woman. 

    2.1. Human reproductive systems

    The diagrams below represent male and female reproductive system.

    Observe and use them to answer questions that follow. 


    a) Identify the structures representing a male and female human
    reproductive system.
    b) Use the choice in (a) to locate and suggest the function of the following
    male human reproductive organs on the diagram: testis, epididymis,
    vas deferens, seminal vesicles and prostate gland.
    c) Use the choice indicating the female human reproductive system
    to locate and suggest the function of the following female human
    reproductive organs on the diagram: urethra, vagina, uterus, ovaries

    and oviducts.

    Human beings reproduce by sexual means where the male and female involve
    in sexual intercourse, resulting in fertilization. During sexual intercourse, the
    interaction between the male and female reproductive systems results in
    fertilization of the woman’s ovum by the man’s sperm. The ovum and sperm are
    specialized reproductive cells called gametes, generated by a process called

    gametogenesis (i.e., spermatogenesis in males and oogenesis in females). 

    2.1.1. Structure of male reproductive system
    The main visible differences between boys and girls at birth are their reproductive
    organs. The sex of a child is determined at the time of fertilization of the ovum by
    the spermatozoon. The differences between a male and a female are genetically

    determined by the chromosomes that each possesses in the nuclei of the cells.


    The male gonads are paired testes, which are suspended within the sacs of
    the scrotum. The testes begin their development inside the abdominal cavity,
    but they descend into the scrotal sacs as development proceeds. If the testes
    do not descend and the male does not receive hormone therapy or undergo
    surgery to place the testes in the scrotum results in sterility (the inability to
    produce offspring). Sterility occurs because undescended testes developing
    in the body cavity are subject to higher body temperatures than those in the
    scrotum. A cooler temperature is critical for the normal development of sperm.

    Sperm produced in the seminiferous tubules of the testes mature within the
    epididymides (sing., epididymis), which are tightly coiled tubules lying just
    outside the testes. Maturation seems to be required for the sperm to swim to

    the egg. 

    Once the sperm have matured, they are propelled into the vasa deferentia
    (sing., vas deferens) by muscularcontractions. Sperm are stored in both the
    epididymides and the vasa deferentia. When a male becomes sexually aroused,
    sperm enter the ejaculatory ducts and then the urethra, part of which is located

    within the penis. 

    The penis is the male organ of sexual intercourse. The penis has a long shaft
    and an enlarged tip called the glans penis. The glans penis is normally covered
    by a layer of skin called the foreskin. Circumcision, the surgical removal of the

    foreskin, is often done soon after birth. 

    In addition to these organs, the male reproductive system consists of a series of
    ducts and glands. Ducts include the vas deferens and ejaculatory ducts. They
    transport sperm from the epididymis to the urethra in the penis.
    Glands include the seminal vesicles, prostate gland, and bulbourethral glands
    (also called Cowper’s glands). They secrete substances that become part of

    semen.

    - Two seminal vesicles contribute about 60% of the volume of semen.
    The fluid from the seminal vesicles is thick, yellowish, and alkaline. It
    contains mucus, the sugar fructose (which provides most of the sperm’s
    energy), a coagulating enzyme, ascorbic acid, and local regulators called
    prostaglandins. 
    - The prostate gland secretes its products directly into the urethra through
    several small ducts. This fluid is thin and milky; it contains anticoagulant
    enzymes and citrate (a sperm nutrient).

    - The bulbourethral glands are a pair of small glands along the urethra below
    the prostate. Before ejaculation, they secrete clear mucus that neutralizes
    any acidic urine remaining in the urethra. Bulbourethral fluid also carries
    some sperm released before ejaculation, which is one reason for the high

    failure rate of the withdrawal method of birth control (coitus interruptus).

    Semen is the fluid that is ejaculated from the urethra. Semen contains secretions
    from the glands as well as sperm. The secretions control pH and provide the

    sperm with nutrients for energy.

    Table 2.1: Parts of the male reproductive system and their functions


    Note: Male infertility refers to a male’s inability to cause pregnancy in a fertile
    female. In humans it accounts for 40-50% of infertility. It affects approximately
    7% of all man. Male infertility may be due to:
    - Absence of sperms in the semen (Azoospermia).
    - Low sperm count e.g. when ones ejaculate less than 1cm3 of semen.
    - Abnormal sperm e.g. sperms with 2 tails, or without tail, or without
    acrosomes,
    - Auto-immunity e.g. antibodies attack one’s sperms
    - Premature ejaculation: the man has orgasm before copulation
    - Impotence i.e. inability to achieve or maintain an erection of the penis.

    2.1.2. Structure of female reproductive system

    The female reproductive system is a collection of organs and other structures
    located primarily in the pelvic region. Most of the structures are inside the body.
    It includes the ovaries, the oviducts, the uterus, and the vagina. The female
    reproductive system has several functions:
    - Producing eggs, which are female gametes
    - Secreting female sex hormones
    - Receiving sperm during sexual intercourse
    - Supporting the development of a fetus
    - Delivering a baby during birth
    During puberty, a girl develops into a sexually mature woman, capable of

    producing eggs and reproducing.


    The external genital organs of a female are known collectively as the vulva. The
    pubic hairs and two folds of skin called labia minora and labia majora are
    on either side of the urethral and vaginal openings. Beneath the labia majora,
    pea-sized greater vestibular glands (Bartholin glands) open on either side of the

    vagina. They keep the vulva moist and lubricated during intercourse.

    At the juncture of the labia minora is the clitoris, which is homologous to the
    penis in males. The clitoris has a shaft of erectile tissue and is capped by a peashaped glans. The many sensory receptors of the clitoris allow it to function
    as a sexually sensitive organ. The clitoris has twice as many nerve endings as
    the penis. Orgasm in the female is a release of neuromuscular tension in the
    muscles of the genital area, vagina, and uterus.

    Table 2.2: Parts of the female reproductive system and their functions



    Note: Female infertility is defined as the inability to conceive or carry a pregnancy
    to term after 12 months of unprotected intercourse, or 6 months of unprotected
    intercourse if the female is over 35 years old. In females, infertility may be due
    to:
    - Failure to ovulate due to the lack of some hormones.
    - Damage of the Fallopian tubes / oviducts, for example the tubes may be
    completely blocked by nature or after an infection.
    - Damage on the uterus; for example, the endometrium can be destroyed.
    - Damage on the cervix, for example the cervix may be narrow or too wide or
    may stop producing cervical mucus needed for the sperm to reach uterus.
    - Antibodies against sperms, for example, the cervix, the uterus or the oviduct

    of a woman can produce antibodies against her husband’s sperms.

    Application activity 2.1
    The figure below represents the male reproductive system.


    a) Justify why it is representing a male reproductive system.
    b) Refer to the figure and identify the parts represented by the numbers
    1 to 8.
    c) How can you justify the function of organ 2, 5 and 7 according to the

    structure of male reproductive system?

    2.1.3. Gametogenesis
    Activity 2.2

    Gametes are haploid cells that are formed from diploid germ cells through
    the process of gametogenesis. The significance of developing haploid
    gametes lies in the fact that after fertilization, the developing zygote attains
    the diploid status back. In this way, the developing embryo gets the single
    copy of all the chromosomes from each parent.
    Based on the chart diagrams of spermatogenesis and oogenesis shown
    below.
    i) Compute the number of chromosomes at each stage, assuming 2n

    = 46. 


    ii) Which diagram does it represent spermatogenesis and oogenesis?

    Explain why?

    A) Spermatogenesis
    The process of formation of haploid male gametes or spermatozoa from diploid
    reproductive cells in males is called spermatogenesis. The complete process is
    broadly divided into two parts, formation of spermatids and spermatogenesis

    or spermatoleosis.

     Formation of Spermatids
    The process of formation of spermatids is further divided into three stages as:
    a) Multiplication phase: The primordial germ cells or sperm mother cells
    differentiate from germinal epithelium of testis and increase in size with
    prominent nuclei. These cells divide repeatedly by mitosis (i.e., equational
    division) and produce a number of diploid daughter cells, known as
    spermatogonia. Thus, in this stage, multiplication of germ cells takes place
    mitotically.
    b) Growth phase: In this phase, spermatogonia increase in size by
    accumulating food reserves and are now called primary spermatocytes.
    c) Maturation phase: The primary spermatocytes (which are diploid)
    undergo first maturation division which is meiotic division (or
    reductional division) to produce two haploid secondary spermatocytes.
    These haploid secondary spermatocytes divide further by mitosis to give
    rise to four haploid spermatids. This mitotic division is called second

    maturation division.

    The spermatids so produced are non-motile rounded structures that
    metamorphose into functional and motile spermatozoa through a process
    known as spermiogenesis or spermatoleosis. The spermatozoa from testis
    are incapable of fertilizing an ovum. They undergo several morphological,
    physiological and biochemical changes as they move through the epididymis
    to attain this structural and physiological maturity. The epididymis i) provides a
    favorable environment to spermatozoa in acquiring fertilizing ability and ii) stores
    them until they are ejaculated or move down to the vas deferens.

    The morphological changes include structural remodeling of acrosome and
    formation of disulfide linkages. The physiological and biochemical changes
    include increase in net negative charge on spermatozoa, change in pattern of
    motility, change in content of sialic acid, increase in specific activity and reflection

    power, resistance to pH and temperature and changes in metabolic patterns.

    – Spermiogenesis
    A series of changes in spermiogenesis that transform a non-motile spermatid
    into motile, functional spermatozoa are listed below:
    - The nucleus shrinks and flattens by losing water. Only DNA is left in the
    nucleus, making cells very light that aids to its motility.
    - The two centrioles of a centrosome form proximal and distal centrioles
    that lie at the posterior end of nucleus and give rise to axial filament of the
    flagellum and acts as a basal granule respectively.
    - The mitochondria gather around axial filament and gradually unite to
    form spiral sheath or nebenkern. It acts as power house of the sperm and
    provides energy.
    - The golgi bodies form the covering over nucleus called acrosome. During
    acrosome formation, one or more vacuoles start enlarging with a small,
    dense body called pro-acrosomal granule which further enlarges to
    form acrosomal granule. The vacuole loses its liquid content and forms the
    cap of spermatozoan. The remaining part of golgi apparatus is reduced
    and discarded from sperm.
    During all these steps, head of the developing sperm remains embedded in
    sertoli cells for nourishment. At the end, fully formed spermatozoan shows

    distinct head, middle piece and tail region.



     Structure of Spermatozoa
    The sperms are microscopic and motile cell. Each sperm is composed of four
    parts a head, a neck, a middle piece and a tail. A plasma membrane covers the
    whole body of sperm.

    i) Head is the enlarged end of the sperm, containing an elongated haploid
    nucleus. The anterior of the nucleus is covered by a cap-like structure called
    acrosome. The acrosome contains enzymes sperm or hyaluronidases,
    which are used to contact and penetrate the ovum at the time of

    fertilization.

    ii) Neck is very short and is present between the head and middle piece. It
    contains the proximal centriole towards the nucleus which plays a role in
    the first cleavage of the zygote and the distal centriole which gives rise to

    the axial filament of the sperm.


    iii) Middle piece possesses numerous mitochondria which produce
    energy for the movement of the sperm. At the end of the middle
    piece, there is a ring centriole (annulus) with unknown function.
    iv) Tail is several times longer than the head. It consists of an axial filament
    surrounded by a thin layer of cytoplasm. The tail provides motility to

    the sperm, which is essential for fertilization.

    b) Growth and differentiation phase: During this long phase, which may
    last upto years, one cell in a follicle prepares for the formation of ovum. It
    starts meiotic division but gets arrested at prophase-I stage and is called
    primary oocyte. The remaining cells of the follicle lose the potential to
    become primary oocyte and are known as the follicular cells or granulosa
    cells. These follicular cells serve to protect and nourish the primary oocyte.
    The complete follicle with a primary oocyte surrounded by a layer of
    follicular cells is called the primary or the ovarian follicle.

    c) Maturation phase: At puberty, only one of the primary oocytes resumes
    division per menstrual cycle, alternately in each ovary. The tertiary follicle
    matures into a Graafian follicle, within which the primary oocyte makes two
    successive to form secondary oocyte. However, the secondary oocyte
    again gets arrested at metaphase stage of meiosis-II and is released
    from the ovary during ovulation. It waits in the oviduct for the sperm to
    arrive. If fertilization occurs, sperm entry into the secondary oocyte marks
    the resumption of meiosis. The 2nd maturation division (meiosis-II) again
    divides the secondary oocyte into two unequal daughter cells: a large
    ootid and a very small 2nd polar body. The ootid undergoes maturation into
    a functional haploid ovum. A thin vitelline membrane develops outside the

    plasma membrane of the ovum that protects and nourishes the latter.

    – Structure of Ovum

    An ovum is a spherical, non-motile cell, in the secondary oocyte stage of
    oogenesis. Human ovum is microlecithal with large amount of cytoplasm.
    Cytoplasm is differentiated into outer, smaller and transparent exoplasm or egg
    cortex and inner, larger and opaque endoplasm or ooplasm. Egg cortex is with
    some cytoskeletal structures like microtubules and microfilaments, pigment
    granules and cortical granules of mucopolysaccharides. Endoplasm is with cellorganelles,
     informosomes, tRNAs, histones, enzymes etc.

    The ovum is covered over by a thin, transparent vitelline membrane which is
    further covered over by zona pellucida. There is a narrow space between these
    two membranes known as perivitelline space. During discharge of ovum from
    the Graafian follicle, several layers of follicular cells adhere to the outer surface

    of zona pellucida and are arranged radially forming corona radiata.


    Table 2.3: Differences between spermatogenesis and oogenesis


    Application activity 2.2
    1. Suppose that four hundred sperm mother cells have undergone a process
    of spermatogenesis in a testis of human. How many chromosomes are
    produced at the end of spermatogenesis? How many chromosomes
    does each sperm have?
    2. On the basis of your observations, use the drawn structure of a human
    spermatozoan and an ovum and label their respective parts along with
    the functions of each:




    2.1.4. Cycle in humans
    Activity 2.3

    Human beings grow and develop from childhood to adulthood, during such
    period of growth and development; there are changes in some parts of body
    which may occur physiologically, physically and even psychologically. These
    changes prepare individual adulthood to reproduce. Different researchers
    indicated these changes to be coordinated by different types of hormones.
    1. Suggest the hormones involved during such period of changes in body
    parts?
    2. Discuss the significance of these hormones you have mentioned above
    during such period of changes.
    3. Describe the role of hormones involved during pregnancy and birth.

    4. Which day of the cycle will ovulation take place?

    The menstrual cycle refers to the periodical changes in the reproductive behaviour
    of a female which tend to occur in a sequence of events one after the other
    in the periodical circle. At the onset of puberty, the cycle begins and repeats
    after 28 days unless interrupted by pregnancy. The changes are stimulated
    by the gonadotrophic hormone such as; follicle stimulating hormone (FSH)
    and luteinizing hormone (LH). These hormones stimulate ovaries to secrete;
    oestrogen (steroid) and progesterone hormones. These four hormones are
    involved in menstrual cycle. Two of them including; FSH and LH are produced
    by pituitary gland and the other two are released by ovaries respectively. The
    most obvious sign of the cycle is the monthly discharge of blood a process
    called menstruation. The first day of menstruation is regarded as the first day

    of the cycle.

    The three phases of the menstrual cycle are the follicular phase, 

    ovulation and the luteal phase.

    a. Follicular phase

    Menstrual cycle usually begins when blood is first discharged from the uterus
    during the first to fifth day (1-5 days). Following the reduction of progesterone,
    the hypothalamus releases gonadotropin releasing hormone (GnRH) which
    stimulates anterior pituitary gland to secrete follicle stimulating hormone (FSH).
    FSH brings about the following effects:
    - Stimulates the development of a primary follicle

    - Contributes to the shedding of uterine wall

     Causes production of oestrogen by uterine cells. The oestrogen produced
    promotes healing, repair and growth of uterine lining, inhibits further
    secretion of FSH. Oestrogen levels keep on raising until day 13 where
    they stimulate secretion of luteinizing hormone (LH) by anterior pituitary

    gland.

    b. Ovulatory phase
    Around the 14th day, the high levels of oestrogen causes release of luteinizing
    hormone (LH).The release of LH brings about ovulation (release of mature egg
    from the ovary). Immediately after and slightly before ovulation, a woman is fertile
    and can conceive a baby if she has sexual intercourse or if sperm is present in

    her oviduct.

    c. Luteal phase
    After ovulation, the remains of ovarian follicle form corpus luteum also known
    as Yellow body, which secrete large amounts of progesterone hormone
    and smaller oestrogen. These two hormones; stimulate further development
    of mammary glands, inhibit release of FSH and thickening wall of uterus in
    anticipation of pregnancy. If oocyte (ovum) is not fertilized with in about 36
    hours of being shed into oviduct, it dies and corpus luteum gets smaller. Thus
    levels of progesterone and oestrogen keep on reducing until day 28 days i.e. 14
    days after ovulation. Low levels of progesterone remove the inhibitory effect on

    FSH, causing its release thus menstruation and the cycle starts again. 


    The menstrual cycle is the regular natural changes that occurs in the female
    reproductive system (specifically the uterus and ovaries) that makes pregnancy
    possible. The cycle is required for the production of oocytes, and for the
    preparation of the uterus for pregnancy. The uterine events during menstrual

    cycle can also be divided into three phases:

    Menstrual phase: when endometrium tissue is discharged and vaginal bleeding
    occurs at the end of ovulatory cycle if pregnancy has not occurred. It is called
    menstruation. It describes the shedding of endometrium when implantation
    does not occur. When pregnancy does not occur, the level of progesterone
    falls and this leads to the shedding of endometrium. Menstrual bleeding lasts
    between 3 and 5 days. The first day of the period is the first day of the cycle. 

    Proliferative phase: It stimulates the thickening of endometrium of the uterus.
    This thickness of endometrium is stimulated by estrogen from follicles before
    ovulation which occurs when the ovarian follicles rupture and release the
    secondary oocyte ovarian cells. This results to the development of ovary. It acts
    like follicular phase.

    Secretory phase: it occurs after ovulation for describes further thickening of
    endometrium (endometrium tissue become more complex) in preparation for
    implantation. This is stimulated by progesterone which is secreted by corpus
    luteum and this occurs when corpus luteum is functioning. It acts like lacteal

    phase.



                            Figure 2.6: Menstrual cycle of human female
    Application activity 2.3
    1. The diagram below represents a section through a human ovary in

    ovulation. 


    1. Use the diagram to locate the step at which ovulation take place. Explain
    your answer.
    2. State what will happen to this structure next if pregnancy has not
    occurred.
    3. State which hormone is needed to cause the changes seen in the

    diagram and indicated by the sequence (1), (2) and (3).

    2.1.5. Fertilization and fatal development

    Activity 2.4

    The following diagram represents different stages that happen before fetal
    development. Use it to answer related questions.


    i) Suggest the name of the cell labeled A.
    ii) Name the process which is happening on the cell labeled B. What
    are the conditions required for the process to happen? Justify your
    answer.
    iii) Describe the process which is happening in C and what happens

    after?

    a. Copulation
    It is act of mating where sperms from male are transferred into the female tract.
    Male mammals have an intromittent organ called penis which becomes erect
    at a moment of mating for insertion into female’s vagina. The erection of penis is
    brought by hydraulic action (penis becomes gorged with blood). This occurs as
    a result of sexual arousal which brings about by ejaculation (release of sperm).
    The semen’s are secreted from accessory glands into vas deferens and bladder
    sphincter closes preventing urine from entering urethra. Sperms are expelled 
    from epididymis into vas deferens and out of the body by a series of muscle
    contraction of penis. In a female, sexual arousal results in the swelling of clitoris
    and stimulates the secretion of mucus which lubricates vagina during sexual

    intercourse.

    b. Fertilization

    Fertilization is the fusion of male and female nuclei to form zygote. Copulation
    results in the ejection of spermatozoa into vagina. The spermatozoa swim in the
    watery mucus of vagina and uterus up into the oviduct where the fertilization
    takes place in the upper part of the oviduct. From the vagina or uterus
    spermatozoa propel using energy from mitochondria. If ovulation has already
    taken place, the egg and sperm meet in the upper part of oviduct and once they
    come into contact, acrosome raptures and release lytic enzyme which dissolve
    corona radiata of the egg and soften zona pellucida and vitelline membrane. The
    following processes take place:
    – Capacitation
    This is a stage where by sperm undergoes essential changes while passing
    through female genital track and this takes about 7 hours. These changes
    include the removal of a layer of glycoprotein from outer surface of sperm, by
    enzyme in uterus. Cholesterol also is removed to weaken the membrane.

    – Acrosome reaction
    This involves the releasing of enzyme found in acrosome such as hyaluronidases
    and protease. These enzymes digest corona radiata (narrow path in the follicle
    cells) and the zona pellucida (a protective glycoprotein surrounding the plasma

    membrane of the egg).

     Fusion
    In this stage the head of sperm will fuse with the microvilli surrounding the

    secondary oocyte and penetrate its cytoplasm.

    – Cortical reaction
    This stage involves the releasing of enzymes by lysosomes in cortical granules
    (outer region of the secondary oocytes); the enzymes cause the zona pellucida
    to thicken and harden forming a fertilization membrane. This cortical reaction
    prevents the entry of other sperm inside ovum (polyspermy).

    – Zygote formation

    The secondary oocyte is stimulated to complete meiosis II, during this time of
    stimulation the nucleus of sperm and secondary oocyte are called pro-nuclei

    and then the two nuclei fuse to form the zygote (2n).


    2.1.6. Embryonic development

    The zygote spends the next few days travelling down the oviduct (Fallopian
    tube) by peristaltic contraction and by beatings of the cilia in wall of the oviduct
    toward the uterus. As it travels, it divides by mitosis several times to form a ball
    of cells called a morula. The cell divisions, which are called cleavage, increase
    the number of cells but not their overall size. More cell divisions occur, and soon
    a fluid-filled cavity forms inside the ball of cells. At this stage, the ball of cells is

    called a blastocyst. 

    The blastocyst reaches the uterus and becomes embedded in the endometrium
    at roughly the 5th – 10th day. Once in the uterus, the blastocyst burrows into the
    uterine wall a process called implantation. After implantation, the blastocyst
    becomes embryo. It grows through multiplication and differentiation of its cells
    forming tissues and organs. The heart and blood vessels are the first organs

    formed and embryo now called foetus.

    During embryonic development, cells of the embryo migrate to form three distinct
    cell layers: the ectoderm, mesoderm, and endoderm. Each layer will eventually
    develop into certain types of tissues and cells in the body of vertebrates.
    - Ectoderm: forms tissues that cover the outer body; develops into cells
    such as nerves skin, hair, and nails.
    - Mesoderm: forms tissues that provide movement and support; develops
    into cells such as muscles, bones, teeth, and blood.
    - Endoderm: forms tissues involved in digestion and breathing; develop

    into organs such as lungs, liver, pancreas, and gall bladder.


    Application activity 2.4

    The diagram below shows some of the events which take place in the ovary

    and oviduct (Fallopian tube) around the time of fertilization.


    a) Name the following:
    i) The process labeled A.
    ii) The type of nuclear division taking place at D and E.
    iii) The structure labeled X.
    iv) One hormone produced by structure X.
    b) On the diagram, use the letter F to label the region where fertilization

    took place

    2.1.7. Role of placenta in the development of an embryo

    Activity 2.5

    The drawing below shows a developing human fetus inside the uterus.

    Observe the diagram and attempt the related questions.


    a) Suggest the name of the parts marked A to D.
    b) Which part is involved in transport of substance from mother to fetus
    on the diagram and why?
    c) Suggest four substances which pass from the mother to the embryo.
    d) Name one substance which passes from the embryo to the mother.

    e) What is the importance of the placenta?

    The placenta is a temporary organ in which nutrients and wastes are exchanged
    between the mother and the embryo or foetus.

    The foetal part of the placenta consists of the allantoids and chorion. The
    chorion forms many large projections called chorionic villi which contain a
    dense network of foetal capillaries which in turn are connected to two umbilical
    arteries and umbilical vein in the umbilical cord. The umbilical arteries carry
    blood from the foetus to the placenta, while the umbilical vein carries blood
    in the opposite direction. Although maternal blood in the endometrium is in
    close proximity with the foetal blood in the umbilical capillaries, they do not mix

    because they separated by membranes of the villi and capillary.


    The placenta is an organ that develops in your uterus during pregnancy with
    specifically the following functions:
    - It allows diffusion of nutrients such as water, glucose, amino acids, simple
    proteins and mineral salts from maternal blood.
    - It is a site of gaseous exchange: haemoglobin of the foetus has high affinity
    to oxygen compared to adult haemoglobin.
    - It offers passive natural immunity on the foetus. Certain maternal antibodies
    can cross the placental barrier.
    - It protects foetal circulation from the high pressure in the maternal
    circulation
    - Prevents mixing of maternal and foetal blood which would cause
    agglutination (clotting) if the two blood types are incompatible.
    - It produces and secretes hormones such as the HCG (human chorionic

    gonadotrophin), progesterone, oestrogen, and relaxin. 

    Note: The action of HCG is similar to that of LH. HCG stimulates the corpus
    luteum to secrete progesterone and oestrogen throughout the first trimester.
    HCG is produced in such large quantities that some of it is excreted in the urine
    of a pregnant woman (positive test of pregnancy). Secretion of HCG declines

    around tenth week and the corpus luteum reduces.

    The placenta does not give complete protection to the foetus. Certain pathogens,
    toxins, and drugs can enter the foetal circulation and cause damage. Examples

    are; HIV, rubella toxins, alcohol, nicotine and heroin.

    Application activity 2.5

    The diagram shows the structure of the placenta and parts of the fetal and

    maternal circulatory systems.


    a) Complete the table by listing the blood vessels that carry oxygenated

    blood. Use the letters in the diagram to identify the blood vessels.


    b) What happens on the structure T after birth?
    c) The placenta is adapted for the exchange of substances between the
    maternal blood and the fetal blood. Describe the exchanges that occur

    across the placenta to keep the fetus alive and well.

    2.1.8. Physiological changes in females during pregnancy
    and Parental care
    Activity 2.6

    Observe the following images that show pregnant women.


    Use your personal observation or conduct research from medical personnel,
    internet or library to answer the following questions:
    a) Suggest the physical changes that can be observed to the pregnant
    women.
    b) What physiological and behavioral changes that can happen when
    women get pregnant.
    c) It is necessary to practice a special parental care to pregnant women.

    Provide reasons that justify this statement.

    Pregnancy refers to the development that take place between fertilization of the
    ovum to birth of the foetus. When fertilized egg becomes implanted in uterine
    wall, pregnancy starts. And a number of important events take place during
    this period. The period from fertilization to birth is called gestation period. In

    human it is about nine months. 

    A. Changes during pregnancy
    A pregnant woman’s body undergoes various; physiological, physical and
    behavioural changes.
    a) Physiological changes during pregnancy
    - Respiration rate rises for increased maternal oxygen consumption which is
    needed for demand of placenta, uterus and foetus.
    - More blood vessels grow and pressure of expanding uterus on large veins
    causes blood to slow in its return to the heart.
    - Rise up and out of pelvic cavity this action displaces the stomach and
    intestine.
    - Blood volume increase greatly.
    - Placenta produces large amount of progesterone and oestrogen by 10 to

    12 week of pregnancy to control uterine activity.

    - Increased requirement of calcium due to increase of parathyroid gland.
    - Experiences warm (hot flashes) caused by basal metabolic rate and
    increased hormonal level.
    - Stretching of abdomen wall and ligaments that support uterus.
    - Kidney work extra hard to excrete waste products of both mother and

    foetus.

    b) Physical changes during pregnancy
    - Breast may become large and more tender because of increased level of
    oestrogen hormone progesterone thus breast gets even bigger to prepare
    for breast feeding.
    - Nipples may stick out more.
    - By the end of third trimester, a yellow, watery, pre-milk may leak from
    nipples.
    - Changes in hair and nail growth and texture due to hormone changes.
    - Leg cramp caused by fatigue from carrying pregnant weight.
    - Feet and ankles may swell because of extra fluid in the body during

    pregnancy.

    c) Behavioural changes during pregnancy
    - Physical discomfort such as urinary frequency can be frustrating.
    - Fear and anxiety lessen especially when foetal movements are felt.
    - Self-introspection
    - Nesting behaviour begins. Some woman exhibits mood swings and

    emotional liability.

    B. Delivery process
    By the end of pregnancy, near the time of birth, the amniotic sac raptures
    (breaks) and amniotic fluid drains through birth canal and labour usually begins
    which involves the contractions of muscular walls of the uterus.

    Initiation of birth: Uterine contractions start when the foetal pituitary gland
    secretes adrenocorticotrophic hormone (ACTH) which stimulates foetal adrenal
    gland to secrete corticosteroids. These hormones pass into blood sinuses in
    placenta to cause maternal cells to secrete prostaglandins (local hormone) and
    cause uterine wall to contract. This contraction pushes the foetal head against
    the cervix to stimulating stretcher receptor to send information to mother’s
    brain and causes release of oxytocin hormone. The prostaglandin and oxytocin
    hormone together result intense contraction of uterine walls called labour
    which stimulates more release of oxytocin hormone and as positive feedback

    mechanism.

    The delivery process can be summarized into three main stages:
    - Dilation stage: During this stage, water sac filled with amniotic fluid forms
    and precedes the head, widening soft tissue of birth canal, cervix, and
    vagina for canal of constant diameter. The amnion raptures and amniotic
    fluid drains through vagina.
    - The expulsion stage: During this stage, cervix is fully dilated while
    abdominal muscle bear down in supporting rhythmic contraction of uterus
    shorten the uterine wall and baby is pushed into and through the birth
    canal. The head and shoulder align themselves first.
    - Placenta stage: This stage begins with complete expulsion of baby and
    ends with expulsion of foetal membrane. The cord is clamped and cut
    when delivery of baby is complete. This leads carbon dioxide enrichment
    into baby’s blood which activates respiratory centre and baby begins to
    breath with the first cry at the same time foetal circulation changes to

    baby’s own systemic and pulmonary circulation.



    Antenatal care is the care you get from health professionals during your
    pregnancy. It is sometimes called pregnancy care or maternity care. Prenatal
    care, also known as antenatal care, is a type of preventive healthcare. Its goal
    is to provide regular check-ups that allow doctors or midwives to treat and
    prevent potential health problems throughout the course of the pregnancy and

    to promote healthy lifestyles that benefit both mother and child.

    a) Health needs of the pregnant mother

    The pregnant mother needs to maintain good health status so that she has a
    healthy baby. To remain healthy she needs:
    - To avoid contractions diseases such as malaria, STIs and HIV and AIDS
    as these may harm the foetus.

    - To avoid smoking and drinking alcohol as these interfere with growth and

    development of the foetus, especially brain development.

    - To eat an adequate balanced diet so that she maintains her good health
    and is able to give birth to a healthy baby. Malnourished mothers usually
    give birth to babies who are underweight. Such babies often have growth
    and development problems because they do not eat well and tend to get
    sick often.

    - To attend the ante-natal clinic once a moth so that her health and nutritional
    needs and those of the foetus are monitored. In the ante-natal clinic the
    mother has her weight monitored, blood pressure checked and urine

    checked to establish the level of sugar.

    During the antenatal period, the promotion of the women healthy is the care
    and health of their babies before and after birth. Educating mothers about the
    benefits of good nutrition, adequate rest, good hygiene, family planning and
    exclusive breastfeeding, immunization and other disease prevention measures
    aims to develop women’s knowledge of these issues so they can make better
    decisions affecting their pregnancy outcome and never forget the difficulties

    some women will face in being able to improve their lifestyles.

    b) Nutritional needs of the pregnant mother

    The pregnant mother needs additional nutritional requirements to meet the needs
    of the growing foetus and those of her body. The pregnant mother therefore
    needs to eat additional balanced diet to cater for these additional nutritional
    requirements in her own body and for that of the growing foetus. The mother
    needs the increased nutrients because of:

    - The increase in the rate at which her body burns energy. More carbohydrates
    and fats are required. Adequate amounts of carbohydrates and fats are
    required for the additional weight the mother puts on. The mother puts on
    additional weight of about 10 to 12.5kg during pregnancy. More energy
    giving foods are required to make up this additional weight.
    - The increase in her blood volume of her additional weight. More iron is
    required to form additional blood required by the body.
    - The development of the placenta which requires nutrients to form and
    making the amniotic fluid within which the foetus grows require more
    nutrients.
    - Increased muscles for both the mother and the growing foetus. The
    mother’s body requires additional muscles, especially the breast and
    uterine tissues. More proteins are required to develop these muscles.
    - The need to store more fat. This fat is stored during the first four months
    of pregnancy. From 5-9 months the stored nutrients are used by the fast
    growing foetus. The mother starts to appear thinner.

    - Preparation of breast-feeding. Nutrients are required  to prepare milk to be

    used to breast-feed the baby.

    The breast milk contains antibodies that help your baby fight of viruses and
    bacteria. Breastfeeding lowers your baby’s risk of having asthma or allergies.
    Plus, babies who are breastfed exclusively for the first 6 months, without any
    formula, have fewer ear infections, respiratory illnesses, and bouts of diarrhea.
    In humans breastfeeding is associated with many other benefits:
    - It makes earlier a closer contact between the mother and her infant
    - The infant has a better control over its own milk intake, this prevents over
    eating in late life
    - Fats and irons from breast milk are better absorbed than those in cow’s
    milk and milk is easily digested.
    - Breast feeding provides important antibodies that help to prevent
    respiratory infections and meningitis,
    - Breastfeeding helps the mother’s reproduction organ return to a normal
    state more rapidly
    - Breast feeding promotes the secretion of LH (and prolactin) and this
    makes a delay in follicle development and ovulation,
    - The act of sucking on the breasts, promotes the development of the jaw,

    facial muscles and teeth (sucking from a bottle requires less effort).

    Application activity 2.6

    1. Copy and complete the table to show, for each hormone, the precise
    site of its secretion, and its effects on the ovary or on the endometrium

    of the uterus.


    Alcohol consumption for pregnant women is generally more dangerous on

    an embryo than a fetus. Suggest the reasons.

    2.2. Family planning and contraceptive methods
    Activity 2.7

    The photos below show various contraceptive methods. 


    a) Use the photos to identify the letters that represent natural and artificial
    contraceptive methods. Justify your choice.
    b) The most effective contraceptive method for young people is the use

    of condom. Provide the reasons for this statement.

    Contraception is the prevention of conception that is preventing the fusion of
    the male gamete with the female gamete. Both natural and artificial methods

    exist.

    2.2.1 Natural contraceptive methods
    Natural birth control methods include specific actions that people can do
    naturally to help prevent an unintended pregnancy. Instead, these methods to
    prevent pregnancy require that a man and woman not have sexual intercourse
    during the time when an egg is available to be fertilized by a sperm.

    The fertility awareness methods are based upon knowing when a woman
    ovulates each month. In order to use a fertility awareness method, it is necessary
    to watch for the signs and symptoms that indicate if ovulation has occurred or

    is about to occur.

    i) Calendar rhythm method

    The calendar rhythm method to avoid pregnancy relies upon calculating a
    woman’s fertile period on the calendar. Based upon her 12 previous menstrual
    cycles, a woman subtracts l8 days from her shortest menstrual cycle to determine 
    her first fertile day, and 11 days from her longest menstrual cycle to determine
    her last fertile day. She can then calculate the total number of days during which
    she may ovulate. If a woman’s menstrual cycles are quite irregular from month to
    month, there will be a greater number of days during which she might become
    pregnant.

    The calendar method is only about 80% effective in preventing pregnancy and
    when used alone, it is considered outdated and ineffective.

    ii) Basal body temperature method

    The basal body temperature (BBT) method is based upon the fact that a
    woman’s temperature drops 12 to 24 hours before an egg is released from her
    ovary and then increases again once the egg has been released. Unfortunately,
    this temperature difference is not very large. It is less than 1-degree F (about a

    half degree C) when the body is at rest.

    The basal body temperature method requires that a woman take her temperature
    every morning before she gets out of bed. A special thermometer that is more
    accurate and sensitive than a typical oral thermometer must be used, and the daily
    temperature variations carefully noted. This must be done every month. Online

    calculators are available to help a woman chart her basal body temperature.

    To use the basal body temperature as a birth control method, a woman should
    refrain from having sexual intercourse from the time her temperature drops until

    at least 48 to72 hours after her temperature increases again.

    iii) Mucus inspection method

    The mucus inspection method depends on the presence or absence of a
    particular type of cervical mucus that a woman produces in response to
    estrogen. A woman will generate larger amounts of more watery mucus than
    usual (like raw egg white) just before release of an egg from her ovary. 

    This socalled egg-white cervical mucus stretches for up to an inch when pulled apart.

    A woman can learn to recognize differences in the quantity and quality of her
    cervical mucus by examining its appearance on her underwear, pads, and toilet
    tissue; or she may gently remove a sample of mucus from the vaginal opening
    using two fingers. She may choose to have intercourse between the time of her
    last menstrual period and the time of change in the cervical mucus. During this
    period, it is recommended that she have sexual intercourse only every other day
    because the presence of seminal fluid makes it more difficult to determine the
    nature of her cervical mucus. If the woman does not wish to become pregnant,
    she should not have sexual intercourse at all for 3 to 4 days after she notices the

    change in her cervical mucus.

    iv) Withdrawal method
    Withdrawal is a behavioral action where a man pulls his penis out of the vagina
    before he ejaculates. The withdrawal method also relies on complete selfcontrol. 
    You must have an exact sense of timing to withdraw your penis in time.

    Because this can be difficult for the man to complete successfully, the withdrawal

    method is only about 75%-80% effective in preventing pregnancy.

    v) Abstinence

    Abstinence from sexual activity means not having any sexual intercourse at all.
    No sexual intercourse with a member of the opposite sex means that there is no

    chance that a man’s sperm can fertilize a woman’s egg.

    vi) Lactation amenorrhea method

    Lactation Amenorrhea method can postpone ovulation for up to 6 months after
    giving birth. This natural birth control method works because the hormone
    required to stimulate milk production prevents the release of the hormone that
    triggers ovulation. This method is highly effective for the first six months after
    childbirth. The mother has to breastfeed the baby at least every four hours
    during the day and every six hours through the night. She also has to be aware
    of her menstrual period. After six months fertility may return at any time.
    Advantages of natural birth control
    - A woman does not need to take medication or use hormonal manipulation.
    - No procedures or fittings by a physician are required.
    Disadvantages of natural birth control include
    - It can be difficult to estimate or know precisely when a woman is fertile,
    allowing increased chances for unplanned conception.
    - Natural methods are not as effective as some forms of contraception.
    - Ovulation test kits are used by some couples using natural methods of
    contraception, and the cost of these kits is another potential disadvantage.
    - Being unable to have intercourse at certain times of the month is a
    disadvantage for some women.
    2.2.2. Artificial contraceptive methods
    Artificial contraception also known as birth control are medication used to
    prevent pregnancy.

    Oral Contraceptive pills: a chemical method of contraception. One version
    uses a combination of progesterone and oestrogen that inhibits ovulation.

    Others are single hormones that require very careful management when taken.

    Intrauterine device (IUD) the coil is placed inside the uterus an exact
    understanding how this works is unclear. A possible explanation is that it
    ‘irritates’ the endometrium such that rejects implantation of embryos. The device
    is made from plastic or copper and inserted by a doctor. Nevertheless, this
    device is very effective.

    Condom is another mechanical method of contraception that prevents the
    sperm from reaching the egg. Composed of a thin barrier of latex this is placed
    over the erect penis and captures semen on ejaculation. This is also a good

    barrier to prevent the transmission of sexual diseases.

    Cap (diaphragm) is another barrier method again made from latex. The cap is
    placed over the cervix to prevent the entry of sperm in semen. This technique
    requires that the cap is put in position in advance of sexual intercourse and that
    it is used in combination with a spermicidal cream. When used correctly this is
    an effective contraceptive however this is not a barrier against the transmission

    of sexual diseases. 

    Sterilization is a surgical and near permanent solution for contraception such
    as: Vasectomy. In men this involves cutting the vas deferens and prevents sperm
    entering the semen. In this state, man still ejaculates normally and releases
    semen however this does not contain sperm. Tubal ligation involves the cutting
    of fallopian tube so that eggs cannot reach the uterus. In women the surgery cuts

    or ties the oviducts thus preventing sperm from reaching the egg in fertilisation. 

    Advantages and disadvantages of birth control
    Advantages of birth control/contraceptives
    - Gives great protection against unplanned pregnancy if one follows
    instructions.
    - Condoms to some extent protect against pregnancy and STDS.
    - Combinations of pills reduce/prevent cysts in breasts and ovaries.
    - Improved family wellbeing.

    - Improved maternal and infant health.

    - Woman must begin using hormonal contraceptive in advance before they
    become effective.
    - Some women experience several; headaches, breast tenderness, chest
    pain, discharge from vagina, leg cramps and swelling or pain.
    Disadvantages of birth control/contraceptives
    - Necessity of taking medication continually.
    - High cost of medication.
    - Hormonal contraceptive does not protect against STDS.
    - Eggs may fail to mature in the ovary for a woman who uses hormonal
    contraceptives.

    - Woman must remember to take them regularly.

    Application activity 2.7
    1. Determining the fertile period
    Count the number of days of your menstrual cycles and count the number of
    days for 10 consecutive cycles. Choose the cycle with the highest number
    of days and the cycle with the lowest number of days. Subtract 18 from the
    lowest cycle and 11 from the highest cycle.

    Example: Mary has 27 days as her shortest cycle and 36 as her longest
    cycle. She has had her menstruation on 09/08/2019. What will be her fertile
    period?

    2. The diagrams below represent different contraceptive methods.

    i) Use the diagrams to state contraceptive method that can prevent both
    STDs and pregnancy. Justify your answer.
    ii) Suppose you are married, which contraceptive method do you prefer

    to use and why?

    Skills Lab 2
    Pregnancy test
    The HCG Card Pregnancy Test is a rapid chromatographic immune assay for
    the qualitative detection of human chorionic gonadotropin in urine to aid in
    the early detection of pregnancy. The test utilizes a combination of antibodies
    including a monoclonal HCG antibody to selectively detect elevated levels of
    HCG.
    The pregnancy test works by checking the urine for a hormone called human
    chorionic gonadotropin (HCG). The woman body only makes this hormone if
    she pregnant. HCG is released when a fertilized egg attaches to the lining of
    the uterus when pregnancy begins. If pregnancy test is positive, it means that
    woman is pregnant. If the pregnancy test is negative, it means that woman is

    not pregnant. 

    Procedure:
    - Carefully read the instruction included in your test kit before collecting
    your urine sample.
    - Remove the plastic cap to expose the absorbent window.
    - Use collected first morning urine one to two weeks after the first missed
    period.
    - Collect urine in a cup and then dip the indicator stick into the cup to
    measure the HCG hormone level.
    - Hold an indicator stick directly in the urine stream until it is soaked,
    which should take about five seconds.
    - Remove the HCG card pregnancy and make observation.

    - Take conclusion of the observation following the indicated interpretation.

    End Unit Assessment 2
    1. Which of the following do sperm NOT travel through?
    a) Ureter
    b) Urethra
    c) Vas deferens
    d) Epididymis
    2. The placenta in humans is derived from the:
    a) Embryo only
    b) Uterus only
    c) Endometrium and embryo
    d) None of the above
    3. The graph below shows the level of reproductive hormones in the

    blood of an un-named mammal during its reproductive cycle.

    a) Name the hormones labelled (a) to (d)
    b) Give the likely day of the cycle on which ovulation takes place and
    give reasons for your answer.
    4. Answer the following questions:
    a) Define the term fertilization

    b) The diagram below shows the structure of a human sperm.



    i) Explain the part played by the organelle labelled A in the process
    leading to fertilization.
    ii) The acrosome contains an enzyme that breaks down proteins.
    Describe the function of this enzyme in the process leading to
    fertilization.
    5. Which contraceptive methods can protect against sexually transmitted
    diseases / infections?
    6. The diagram shows the sequence of events in the development of a
    mature ovarian (Graafian) follicle and corpus luteum

    a) What is the main hormone produced by the ovary when stage B is
    present?
    b) Which two of stages A to E would you expect to find in the ovary of
    a woman during the early stages of pregnancy?
    c) Give the reason for your answer on b.
    d) Some oral contraceptives contain only estrogens. Which of the
    stages A to E would you expect to find in the ovary of a woman who
    had been taking such an oral contraceptive for a prolonged period of
    time?

    e) Give reasons for your answer on d.

    ◄UNIT 1: BASIC BIOCHEMISTRY OF LIFEUNIT 3: FERTILIZERS ►