L1: First week of development

Question 1

what are the primary male sex organs?

Answer 1

the testis (2 in number).

Question 2

where are the testes?

Answer 2

In the scrotum.

Question 3

what is the function of testes?

Answer 3

produce sperms and secretes male sex hormone.

Question 4

what are secondary male sex organs?

Answer 4

the epididymis, the vas deferens, the seminal vesicles, the ejaculatory ducts, the urethra and the accessory glands (seminal vesicle, prostate and bulbourethral glands).

Question 5

what are male external sex organs?

Answer 5

(scrotum & penis; male copulatory organ).

Question 6

what are female primary sex organs?

Answer 6

the ovaries (2 in number).

Question 7

where are the ovaries?

Answer 7

In the pelvis

Question 8

what is the function of the ovaries?

Answer 8

produce ova and secretes female sex hormones.

Question 9

what are female secondary sex organs?

Answer 9

Uterine tube, uterus, and vagina

Question 10

what are female external sex organs?

Answer 10

the vulva

Question 11

what are the parts of the uterine tube?

Answer 11

formed of 4 parts; infundibulum, ampulla (widest part), isthmus (narrowest part) and intramural part.

Question 12

The uterus

Answer 12

pear-shaped, lies in the pelvis, formed of 3 parts (fundus, body and cervix) and its wall consists of 3 layers (endometrium, myometrium & perimetrium).

Question 13

The vagina

Answer 13

acts as female copulatory and birth canal, its upper end surrounds the cervix which divides it into 4 fornices (anterior, posterior, and 2 lateral).

Question 14

what does a mature sperm consist of?

Answer 14

The mature sperm consists of:
 Head:
- Contains nucleus (has the haploid number of chromosomes; 22 X or 22 Y).
- Covered by acrosome (head cap) which contains enzymes for penetration of the coverings of the ovum.

 Neck.

 Tail: consists of:
- Middle piece (contains mitochondrial sheath which produces energy needed for sperm motility).
- Principal piece (responsible for sperm motility).
- End piece.

Question 15

what does a mature ovum consist of?

Answer 15

 Usually released from the ovary in the stage of 2ry oocyte (contains a haploid number of chromosomes; 22X).
 Surrounded by zona pellucida & corona radiata

Question 16

what is fertilization?

Answer 16

it is the union of the male and female gametes to form the zygote.

Question 17

Where does fertilization take place?

Answer 17

In the ampulla.

Question 18

process of fertilization

Answer 18

deposition

transport of sperms

capacitation

acrosome reaction

Question 19

Deposition

Answer 19

about 200 – 600 million sperms are deposited in the posterior fornix of the vagina during sexual intercourse

Question 20

transport of sperms

Answer 20

about 200 – 300 sperms reach the fertilization site while other sperms die.

Question 21

capacitation

Answer 21

process by which the sperm acquires the capacity to fertilize the ovum and it takes place in the female’s genital tract for 7 hours.

Question 22

what is the mechanism of capacitation?

Answer 22

removal of the seminal plasma proteins from the cell membrane of the head of sperm.

Question 23

acrosome reaction

Answer 23

process by which the sperm releases the contents of its acrosome and it takes place around the ovum.

Question 24

what is the mechanism of acrosome reaction?

Answer 24

release of the following substances:
 Hyal-uronidase enzyme: penetrates the corona radiata.
 Trypsin-like substance: digest the zona pellucida.
 Zona lysine: help the sperm to penetrate the zona pellucida

Question 25

what are the steps of fertilization?

Answer 25

1) Penetration of corona radiata: by hyal-uronidase enzyme.

(2) Penetration of zona pellucida: Trypsin-like substance digests the zona then zona lysine help the sperm to penetrate the zona.

(3) Fusion of the cell membrane of the sperm and ovum: while the head and tail enter the oocyte.

(4) Zona reaction: once the sperm penetrates the zona this reaction occurs make the zona pellucida impermeable to other sperms.

(5) Completion of the 2nd meiotic division: after entry of the sperm the oocyte completes the 2nd meiotic division to give mature ovum (female pronucleus) and 2nd polar body.

(6) Formation of male pro-nucleus: by the nucleus of the sperm.

(7) Union of the pro-nuclei: to form zygote with 46 chromosomes

Question 26

what are the results of fertilization?

Answer 26

1. The 2ry oocyte completes the 2nd meiotic division.
2. Restoration of the diploid number of chromosomes.
3. Determination of the sex of the embryo (if the sperm is Y male and if the sperm is X female).
4. Determination of the state of health and disease of the embryo.
5. The zygote starts cell division (cleavage).

Question 27

what is dispermy(triploidy)?

Answer 27

it is the fertilization of the ovum with two sperms (69 chromosomes)

Question 28

what is parthenogenesis?

Answer 28

it is the dividing of the ovum to form the zygote.

Question 29

what is cleavage?

Answer 29

repeated mitotic divisions of the zygote to increase the number of cells (blastomeres).

Question 30

what is the site of cleavage?

Answer 30

during passage of the zygote in the uterine tube towards the uterus.

Question 31

what are the steps of cleavage?

Answer 31

1. Repeated cell division: the zygote gives 2 then 4 then 8 blastomeres.
2. Formation of morula: after 3 days 16 – 32 blastomeres are formed. They are surrounded by zona pellucida which has the following functions:
    Keep the dividing cells together.
    Prevent adhesion between the dividing cells and the uterine tube.
3. The morula reaches the uterine cavity: about the 4th – 5th day.
4. Formation of blastula (blastocyst):
   - Small cavities filled with fluid (from the uterine cavity) appear in between the dividing cells.

• The cavities fuse together to form one large cavity (Blastocele), which separates the blastomeres into 2 groups:
   Trophoblast: thin outer layer which will form the fetal part of the placenta.
   Inner cell mass: an inner group of cells that will give rise to the embryo.
   The zona pellucida degenerates and disappears.