HUMAN REPRODUCTION Flashcards
1
Q
EXPLAIN THE SCHEMATIC OUTLINE OF THE HUMAN LIFE CYCLE
A
- during meiosis the chromosome number is halved from diploid to haploid
- therefore gametes have the haploid chromosome number
- two haploid gametes fuse during fertilisation to form a diploid zygote
- the zygote develops into a multicellular diploid organism by mitosis
2
Q
EXPLAIN THE FUNCTION OF THE TESTES
A
- produce and release sperm
- produce male sex hormone, testosterone, that plays a role in spermatogenesis and the development of the secondary sexual characteristics
3
Q
EXPLAIN THE FUNCTION OF THE EPIDIDYMIS
A
- temporarily stores sperm produced by the testes until it is mature and ready to fertilise the ovum
4
Q
EXPLAIN THE FUNCTION OF THE VAS DEFERENS
A
transports sperm, by means of peristaltic movements, from the epididymis to the urethra
5
Q
EXPLAIN THE FUNCTION OF THE URETHRA
A
transports both urine and sperm to the exterior
6
Q
EXPLAIN THE FUNCTION OF THE SEMINAL VESICLES
A
- the energy-rich secretion of the mucous membrane provides fructose, the main soruce of food for the sperm
- the secretion also acts as a lubricant enhancing the motility of the sperm cells
7
Q
EXPLAIN THE FUNCTION OF THE PROSTATE GLAND
A
- secretes prostate fluid that acts as a lubricant for the motility of sperm cells, protects sperm against the low pH in the urethra and vagina, protects sperm against infection
8
Q
EXPLAIN THE FUNCTION OF THE COWPER’S GLAND
A
- the secretions of this gland contribute to greater mobility of the sperm
- clears urethra of urine residue
- lubricates the head of penis
9
Q
EXPLAIN THE FUNCTION OF THE PENIS
A
transfers the sperm from the male to the female during copulation
10
Q
EXPLAIN THE FUNCTION OF THE OVARY
A
- produce and release ova
- produces hormones, oestrogen and progesterone
11
Q
EXPLAIN THE FUNCTION OF THE FALLOPIAN TUBES
A
- transports the ovum as well as the developing zygote
- the site of fertilisation and the first divisions of the zygote
12
Q
DESCRIBE THE INTERNAL STRUCTURE OF THE UTERUS
MENTION SPECIFICALY THE ENDOMETRIUM AND THE CERVIX
A
- wall of the uterus consists of three layers, i.e. an outer serous layer, a muscular layer of smooth, involuntary muscle and the endometrium that lines the uterus on the inside
- every month, the endometrium goes through cyclical changes where it thickens by becoming more vascular and glandular in preparation for the implantation of the fertilised ovum
- the uterus narrows and opens to the vagina through the cervix, a neck region rich in glands that secrete cervical mucous
13
Q
LIST THE MAIN CHANGES THAT OCCUR DURING PUBERTY UNDER THE INFLUENCE OF TESTOSTERONE
A
- increased muscle mass
- development of a deeper voice
- enlargement of the penis and sperm
- production of sperm
- development of sexual drive
- increased production of sweat
- increase in facial and body hair
- skin becomes oily
- behavioural changes
14
Q
LIST THE MAIN CHANGES THAT OCCUR DURING PUBERTY UNDER THE INFLUENCE OF OESTROGEN
A
- increase in fat deposited below the skin
- widening of hips
- development of breasts
- increase in height
- development of ova in the ovaries
- start of menstruation
- growth of body hair
- skin becomes more oily
- behavioural changes
15
Q
EXPLAIN THE PROCESS OF SPERMATOGENESIS
A
under the influence of testosterone, diploid cells in the seminiferous tubules of the testes undergo meiosis to form haploid sperm cells
16
Q
EXPLAIN THE PROCESS OF OOGENESIS
A
- diploid cells in the ovary undergo mitosis to form numerous follicles.
- at the onset of puberty and under the influence of FSH one cell inside a follicle enlarges and undergoes meiosis.
- of the four cells that are produced, only one survives to form a mature, haploid ovum.
- this occurs in a monthly cycle.
17
Q
DESCRIBE THE FUNCTIONS OF ALL THE PARTS OF A SPERM CELL
A
- head - contains the haploid cell nucleus with the male genetic material
- acrosome - a sac at the front containing lytic enzymes that digest the protective jelly layer of the ovum to allow the sperm’s head and nucleus to penetrate the ovum’s membrane
- middle portion/neck - contains many mitochondria that provides energy to the tail for locomotion
- tail - performs whip-like movements that propel the sperm through the seminal fluid allowing it to swim towards the ovum
18
Q
DESCRIBE THE FUNCTIONS OF ALL THE PARTS OF AN OVUM
A
- jelly layer - provides protection to the early developmental stages of the fertilised ovum
- haploid cell nucleus contains the female genetic material
- cytoplasm - provides a reserve source of nutrients for the fertilised ovum
19
Q
DEFINE WHAT CYCLES THE MENSTRUAL CYCLE INCLUDES
ALSO INCLUDE THE LENGTH OF CYCLE
A
ovarian cycle and uterine cycle and progresses over a period of 28 days
20
Q
EXPLAIN THE EVENTS THAT LEAD TO THE DEVELOPMENT OF THE GRAAFIAN FOLLICLE
A
- germinal epithelial cells that form the outer layer of the ovary divide by mitosis and form oogonia
- each oogonium is surrounded by a granular layer. the oogonium together with its granular layer is known as the primary follicle
- inside the primary follicle, the oogonia grow into primary oocytes
- at 10-12 years, the hypophysis starts to secrete the hormone FSH, which stimulates development of primary follicles into graafian follicles.
21
Q
EXPLAIN THE EVENTS THAT LEAD TO OVULATION
A
- the developing follicles secrete increasing amounts of oestrogen
- the primary oocyte divides by meiosis 1 into two cells: a larger cell, the secondary oocyte and a smaller cell, the polar body
- the mature graafian follicle moves to the surface of the ovary where it forms a slight protuberance. the follicle increases in size as the production of follicle fluid increases and eventually the wall of the ovary ruptures to release an ovum into the fallopian tube
- this release of an ovum is known as ovulation
22
Q
EXPLAIN THE EVENTS THAT LEAD TO THE FORMATION OF THE CORPUS LUTEUM
A
- after ovulation the remains of the graafian follicle develop under the influence of LH, into a mass of yellow cells known as the corpus luteum
- the corpus luteum secretes progesterone and a little oestrogen to maintain the endometrium for implantation
- if the released ovum is not fertilised, the corpus luteum degenerates until only a small scar remains
- if fertilisation does occur, the corpus luteum continues to function and maintain the endometrium until the 12th week of pregnancy
23
Q
EXPLAIN THE CHANGES THAT TAKE PLACE IN THE THICKNESS OF THE ENDOMETRIUM
A
- the endometrium of the uterus is rich in glands and blood vessels
- from puberty to menopause the endometrium undergoes monthly cyclical changes known as the uterine cycle
- the female hormones oestrogen and progesterone are responsible for thickening the endometrium
- if fertilisation does not occur, the thickened and vascularised tissue of the endometrium is not needed for implantation
24
Q
EXPLAIN THE PROCESS OF MENSTRUATION IN THE UTERINE CYCLE
A
- the upper layers of the endometrium break down; are shed and discarded together with the unfertilised, immature ovum to exit the body via the cervix and vagina
- menstrual blood consists of endometrial tissue, blood and mucous
- lasts for about 4-6 days
- the endometrium in the uterus immediatly starts to thicken once more to prepare for the arrival of the next, possibly fertilised, ovum
- if fertilisation occurs, the corpus luteum remains active and secretes hormones which maintain the endometrium, keeping it thick for implantation
25
DESCRIBE EACH 14 STEPS OF THE **HORMONAL CONTROL OF THE MENSTRUAL CYCLE**
| [file:///C:/Users/sagem/Dropbox/PC/Downloads/Photo.pdf](http://)
1. the hypophysis secretes **FSH**
2. **FSH** stimulates the development of primary follicles in the ovary into mature Graafian follicles
3. developing follicles secrete increasing amounts of **oestrogen**
4. **oestrogen** stimulates the development of a thickened endometrium making it more galndular and vascular in preparation for implantation of a fertilised ovum
5. high levels of **oestrogen** around day 14 stimulate the hypophysis to secrete more **LH** and **FSH** which causes a peak in each hormone
6. high levels of **LH** stimulate the process of ovulation which normally occurs around day 14. during ovulation. the Graafian follicle ruptures to release the ovum into the fallopian tube
7. high levels of **LH** will transform the remnants of the graafian follicle into a corpus luteum
8. the corpus luteum releases large amounts of **progesterone** and small amounts of **oestrogen**
9. **progesterone** and **oestrogen** both play a role in the thickening of the endometrium during the second half of the cycle making the endometrium even more glandular and vascular
10. high levels of **progesterone** and **oestrogen** exert a negative feedback on the pituitary gland and inhibit the release of **FSH** to prevent the development of new follicles and **LH** to prevent ovulation
11. if fertilisation does not occur, the corpus luteum starts degenerating from day 24 of the cycle
12. the shrinking corpus luteum secretes less hormones which leads to a drop in the levels of **progesterone** and **oestrogen**
13. decreasing levels of **progesterone** and **oestrogen** cannot maintain the endometrium and it is shed, with blood, during menstruation
14. the drop in progesterone levels eliminates the negative feedback mechanism on the pituitary gland which leads to an increase in the levels of **FSH**. increasing levels of FSH stimulate the development of a new follicle in the ovary and the entire cycle starts over again.
| FSH = **FOLLICLE STIMULATING HORMONE**, LH = **LUTEINISING HORMONE**
26
EXPLAIN THE NEGATIVE FEEDBACK IN THE PRODUCTION OF OVA
1. increasing levels of oestrogen, secreted by the **developing follicle**, inhibit the release of FSH from the hypophysis. this prevents the development of further follicles in the ovary.
2. increasing levels of progesterone and oestrogen, secreted by the **corpus luteum**, inhibit the release of FSH and LH from the hypophysis. this prevents the development of any other follicles as well as ovulation
3. once the corpus luteum degenerates, **oestrogen** and **progesterone levels** in the blood will drop. therefore, the secretion of FSH and LH is no longer inhibited, their concentration rises, and the process starts over again
27
DEFINE THE TERM **COPULATION**
the erect penis is placed inside the female vagina and semen is released
28
DEFINE THE TERM **FERTILISATION**
the fusion of the haploid nucleus of a sperm with the haploid nucleus of the ovum to form a diploid zygote
29
DESCRIBE THE **PROCESS** OF FERTILISATION
1. the sperm in the semen enter the cervix, pass through the uterus and enter the **fallopian tube**
2. the **ovum** released during ovulation, is normally fertilised in the first third of the fallopian tube
3. the sperm cell propels itself by means of the tail, using the energy from mitochondria in the midpiece and fructose in the semen
4. a large number of sperm surround the ovum and attach to it
5. the acrosome of the sperm secretes **lytic enzymes** that digest the outer layer of follicle cells around the ovum
6. the head of one sperm makes contact with and penetrates the ovum's cell membrane. the tail of the sperm is discarded
7. the ovum's cell membrane becomes **impenetrable** to other sperm cells and is now called the **fertilisation membrane**
8. the **haploid nucleus of the sperm fuses with the haploid nucleus of the mature ovum**. the newly formed diploid nucleus has two sets of chromosomes. one set from the male gamete and one set from the female gamete. this fertilised ovum is now called a **zygote**
30
EXPLAIN THE DEVELOPMENT OF THE
ZYGOTE **-** BLASTOCYST **-** FOETUS
1. the zygote divides by mitosis to form a ball of morula, then undergoes mitosis further to form a hallow ball of cells called a blastocyst
2. the developing egg call is immotile and is transported through the fallopian tube to the uterus by contractions and the cilia
3. takes 5-8 days for the embryo to reach the uterus
4. in the uterus the blastocyst sinks into the endometrium. this process is called implantation
5. after implantation, the blastocyst produces chorionic villi from its outer membrane
6. the chorionic villi grow into the endometrium to form the placenta
7. the placenta is attached to the embryo via the umbilical cord which has 2 umbilical arteries and 1 umbilical vein
8. the embryo is enclosed by the amnion.
9. after 8 weeks, the embryo develops into a foetus
31
DEFINE THE TERM **IMPLANTATION**
when the blastocyst cells becomes embedded in the endometrium. this process is called **implantation**
32
EXPLAIN THE ROLE OF **OESTROGEN** AND **PROGESTERONE** IN MAINTAINING PREGNANCY
1. due to the action of **oestrogen** and **progesterone**, the endometrium is thick and very vascular
2. high levels of progesterone ensure a thick endometrium and thus maintain the pregnancy and prevent menstruation
33
EXPLAIN THE FUNCTION OF THE **CHORION** AND **CHORIONIC VILLI**
1. the chorion develops a rich supply of blood vessels and forms an intimate association with the endometrium
2. the chorionic villi provide an exchange site for the exchange of nutrients and wastes.
34
EXPLAIN THE FUNCTION OF THE **PLACENTA**
THE PLACENTA PERFORMS THE FOLLOWING **FUNCTIONS**:
1. the nutrition of the embryo
2. excretion
3. gaseous exchange
4. acts as a microfilter
5. endocrine function
35
EXPLAIN THE FUNCTION OF THE **UMBILICAL CORD**
1. the two umbilical arteries **carry deoxygenated blood** and waste products from the foetus **to the placenta**
2. the umbilical vein **carries oxygenated blood**, rich in nutrients, from the **placenta to the foetus**
36
EXPLAIN THE FUNCTION OF THE **AMNION**, **AMNIOTIC CAVITY** AND **AMNIOTIC FLUID**
THE AMNIOTIC FLUID PERFORMS THE FOLLOWING **FUNCTIONS**:
1. it provides the **watery medium** in which the foetus can **freely move** and develop
2. it **protects** the foetus from **shocks**, **dehydration** and **temperature changes**
