Draw and label the human male reproductive system
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ii) Describe how the mammalian male reproductive system is adapted to perform its functions
Penis
- is highly vascularised/spongy
- has a sensitive glands
- becomes erect to allow entry into the vagina
Scrotum
- contains the testes outside the body on whose walls the process of spermatogenesis takes place
- the process is favored by lower temperature
- it contains sertoli cells which nourish sperms until they are mature
Epididymis
- long and coiled for the purpose of sperm storage
Vas deferens
- muscular
- upon contraction pushes sperms out and allows ejaculation
Gametes
- produced in large numbers to increase chances of fertilization
- the sperms have a tail for swimming/large number of mitochondria to provide energy/allow swimming to reach the egg
Accessory glands
- are seminal vesicle, Cowper’s gland and prostate gland
- they produce seminal fluid to provide a medium/ nutrients for sperms to swim
iii) How is the sperm adapted to perform its function?
- acrosomes contain enzymes to digest egg membrane
- nucleus contains genetic material
- mitochondria produce energy to move the tail back and forth
- the lashing movement of the tail enables the sperm to move/propulsion in fluid medium towards the egg
- it is streamlined for faster/easier movement/swimming to meet the egg
c) i) Draw and label the human female reproductive system
![](https://highschool.co.ke/wp-content/uploads/2022/09/image-100.png)
![](https://highschool.co.ke/wp-content/uploads/2022/09/image-101.png)
![](https://highschool.co.ke/wp-content/uploads/2022/09/image-102.png)
ii) Describe how the various structures of the human female reproductive system are adapted to their function
Ovaries
- have several graafian follicles that develop and burst open to release/produce mature ova
- secretes sex hormones)oestrogen) which initiate/control development of secondary sexual characteristics
- produce hormones oestrogen and progesterone which prepare the uterus for implantation and subsequent nourishment of the embryo
Oviducts (fallopian tube)
- are thin narrow and tubular to increase flowing speed of semen containing sperms
- are funnel shaped on the end next to ovary which enables them to receive the ovum
- their lining contains cilia which propel the ovum towards the uterus
- has peristaltic muscles that enable movement of zygote/ovum to the uterus for implantation
- is fairly long to increase surface area for fertilization
Uterus
- is muscular for protection of developing embryo
- has elastic wall that allows growth and development of foetus/embryo
- has a highly vascularised endometrium that provides nutrients/gaseous exchange to developing embryo
Cervix
- has valves that close the lower end of the uterus to ensure continued pregnancy during gestation period
- is capable of dilating
- has narrow entrance/neck-like entrance to uterus that enables quick swimming of sperms to uterus
- has suction mechanism that draws up/pulls sperms into uterus
- has a “W” shape that fits well with the glands of the penis to ensure sperms are deposited at the right point
Vagina
- is elastic and muscular to enable good accommodation or penetration of the penis thus proper deposition of sperms and for easy parturition
- allows menstrual flow
- has sensitive labial walls which secrete/produce lubricating substances that ensure/enable/facilitate good coition
- capable of considerable enlargement, due to elastic muscles, to accommodate baby during parturition
Clitoris
- has sensitive cells for orgasm
iii) Explain how the ovum is adapted to its function
- nucleus contains genetic material
- ventelline membrane encloses plasma membrane which encloses yolky cytoplasm
- yolky cytoplasm provides nourishment
- jelly coat protects ovum against dehydration
iv) Explain the differences between sperm and ovum
Sperm | Ovum |
long with a tail and head smalllocomotorystores little foodhas acrosome (tip with lytic enzymes)nucleus prominent but cytoplasm negligible | sphericallargestationarya lot of food stored in yolky cytoplasmlacks acrosomea lot of cytoplasm |
d) i) Explain the process of fertilization
- a process whereby the egg and sperm are brought together and fuse to form a zygote
- occurs in the fallopian tube after copulation
- sperm head penetrates the outer coat of the ovum while the tail remains outside
- penetration is due to reaction of acrosome
- acrosome digests the vitelline membrane
- thereafter a zygote is formed
- zygote which is diploid undergoes rapid cell division to form a mass of cells called blastocyst
- after fertilization a membrane forms around the ovum to prevent further entry of sperms
- blastocyst eventually develops into an embryo
i) Explain the process of implantation
- this is the embedding and attaching of the embryo in the uterine wall/endometrium
- implantation marks the beginning of pregnancy
- sometimes implantation occurs in the oviduct wall which is abnormal and results in ectopic pregnancy which is fatal
- the outer wall of the blastocyst develops fingerlike projections which project into the uterine wall for attachment
- the projections are called villi
- the villi and endometrium develop into an organ that is called the placenta
- the embryo is attached to the placenta through a cord called the umbilical cord
State the functions of umbilical cord
- it contains blood vessels umbilical artery, iliac arteries and umbilical veins)
- it joins the placenta to the embryo
- passage for nutrients from the mother
- passage of excretory substances from foetus to mother for final discharge
- gaseous exchange
- passage of antibodies from mother to foetus, for protection of foetus against diseases
iv) State the role of placenta
- exchange of gases between mother and foetus
- exchange of nutrients and nitrogenous wastes
- anchorage/attachment of foetus
- produces hormones (oestrogen and progesterone)
e) i) What is gestation period?
- time taken from fertilization to birth/pregnancy
ii) Explain the functions of the membranes associated with placenta
Chorion
- surrounds the embryo
- has fingerlike projections that attach embryo to the uterus
Amnion
- contains amniotic fluid
- fluid surrounds embryo
- protects embryo from mechanical injury by acting as shock absorbers
- fluid also protects embryo from dehydration
- distributes pressure equally over embryo
Yolk sac
- surround the yolk
- produces blood cells for embryo until its own liver is able to perform the task
Allantois
- present only for a short time
- removes and store waste material
- it eventually becomes the umbilical cord
iii) Explain the events that take place to facilitate parturition
- near birth the placenta produces less progesterone
- oxytocin hormone is produced by posterior lobe of pituitary gland
- because progesterone level has decreased the uterus becomes sensitive to oxytocin
- oxytocin causes the contraction of the uterus (myometrium)
- these contractions are called labour pains
- just before parturition the head turns downwards
- the contractions eventually push the baby through the vagina
- amnion breaks and amniotic fluid is released
- oxytocin dilates the cervix
- foetus is expelled through cervix with head coming out first
- finally the whole infant comes out
- the umbilical cord is cut and the placenta is expelled as afterbirth
iv) State the reasons why later in pregnancy the ovary will b e removed without disturbing the pregnancy
- corpus luteum in the ovary secretes progesterone which maintains pregnancy and development of foetus after conception
- after four months pregnancy is maintained by progesterone from the placenta
f) i) What are secondary sexual characteristics
– Characteristics (physiological and anatomical) that start developing at puberty due to the influence of male and female hormones
ii) State the main secondary changes in Boys
- deepening of the voice
- growth of hair on face, pubic part, chest, legs
- penis and testes become bigger
- muscular development
- sperm production begins at puberty and may continue throughout life
Girls
- growth of hair on pubic part and armpits
- widening/enlargement of hips
- development of breasts
- menstrual cycle starts as ovaries mature
- body acquires extra fat
iii) Describe the role of hormones in secondary sexual characteristics inBoys
Follicle stimulation hormone (FSH)
- from pituitary
- stimulates production of androgens(male hormones) mainly testosterone by testis
Testosterone
- secondary sexual characteristics
Girls
FHS
- from pituitary
- development of follicles
- stimulates oestrogen production by ovary
LH
- from pituitary
- ovulation
- stimulates release of progesterone by ovary
Oestrogen
- stimulates release of LH
- secondary sexual characteristics
Progesterone
- also from placenta
- sustains pregnancy as it inhibits prolactin and oxytocin during pregnancy
Prolactin
- milk formation
Oxytocin
- parturition
- milk ejection
g) i) What is menstruation?
– vaginal discharge due to disintegration of endometrium
ii) Describe the role of hormones in the human menstrual cycle
- it is controlled by sex hormones which are responsible for the onset of secondary sexual characteristics and also control of the menstrual cycle
- the onset is signaled by discharge of blood/menses 14 days following the start of menstruation
- anterior lobe of pituitary gland secretes follicle stimulating hormone(FSH)
- Follicle stimulating hormone causes graafian follicle to develop in the ovary. It also stimulates tissues of the ovary/wall (theca) to secrete oestrogen
- oestrogen causes repair/healing of uterine wall
- oestrogen stimulates anterior lobe of pituitary to produce luteinising hormonge (LH)
- LH causes ovulation. It also causes graafian follicle to change into corpus luteum. LH stimulates corpus luteum to secrete progesterone
- Progesterone causes proliferation/thickening of uterine wall
- Oesterogen/progesterone inhibits the production of FSH by anterior lobe of pituitary, thus no more follicles develop and oestrogen production reduces
- In the next two weeks progesterone level rises and inhibits production of LH from anterior lobe of pituitary
- The corpus lutetium stops secreting progesterone and menstruation occurs when the level of progesterone drops
- Anterior lobe of pituitary starts secreting FSH again.
iii) What is menopause?
- end of ovulation in women
- occurs after age of 45 years
- does not occur in males