Gametogenesis

Question 1

What similarities do both gametogenesis pathways share?

Answer 1

Both proliferate by mitosis
Reshuffle genetically and reduce to haploid cells via meiosis
Cytodifferentiate into mature gametes

Question 2

What are the main differences between the ovum and sperm?

Answer 2

Females produce very few gametes (400 in a lifetime)
Females produce gametes intermittently (1 per month)
Males produce many (200 million per day) continuously

Question 3

What three features of meiosis ensure genetic variation?

Answer 3

Crossing over
Independent assortment
Random segregation of alleles

Question 4

At what point in meiosis does crossing over occur?

Answer 4

Prophase 1

Question 5

What is the function of the blood testis barrier in males?

Answer 5

Keeps basal and adluminal compartments separate and protects spermatozoa from a host immune response

Question 6

What cells are often referred to as nurse cells?

Answer 6

Sertoli cells. Nurture sperm and precursors

Question 7

What is the purpose of Leydig cells?

Answer 7

Produce testosterone

Question 8

Name the different precursors for spermatozoa throughout spermatogenesis?

Answer 8

Spermatogonium - primary spermocyte- secondary spermocyte - spermatid- spermatozoa

Question 9

What are Ad spermatogonium?

What are Ap spermatogonium?

Answer 9

Ad - resting, reserve stock

Ap - active, maintain stock and produce type B spermatogonia giving rise to new primary spermatocytes

Question 10

What defines spermatogenic cycle?

Answer 10

Time taken for reappearance of the same stage of spermatogenesis within a given segment of a tubule

Question 11

What defined spermatogenic wave?

Answer 11

Distance between the same stage on two different cycles

Question 12

What is spermiation?

Answer 12

Spermatid release into the lumen of seminiferous tubules

Question 13

What is spermiogenesis?

Answer 13

Release of spermatic s into seminiferous tubules (spermiation) and remodelling of sperm as they move to the epidydimis and gain motility.

Question 14

How do the non motile spermatids reach the epididymis?

Answer 14

Transport via Sertoli secretions and peristaltic contraction

Question 15

What is sperm capacitation?

What clinical relevance does this have?

Answer 15

Removal of glycoproteins and cholesterol from sperm membrane to make sperm fertile

In vitro fertilisation requires sperm to be incubated in capacitation media

Question 16

What is atresia?

Answer 16

Cell death and degeneration of primary oocytes in female reproduction

Question 17

What are primordial follicles?

Answer 17

Surviving oocytes that have entered meiosis 1 and are surrounded by flat epithelial follicular cells

Question 18

What occurs in the preantral phase of oogenesis?

Answer 18

Follicular epithelium changes from flat to cuboidal and proliferate to form granulosa cells

Question 19

What occurs in the antral stage of oogenesis?

Answer 19

Fluid filled spaces appear between granulosa cells and coalesce to form the antrum

Question 20

What occurs in the preovulatory phase of oogenesis? (Caused by a surge of LH)

Answer 20

Oocyte completes meiosis 1 forming a polar body, then undergoes meiosis 2 but arrests in metaphase.

Question 21

How does ovulation occur?

Answer 21

Surge in LH causes increased collagenase activity and prostaglandins cause local muscular contraction resulting in oocyte extrusion

Question 22

What is the corpus luteum?

Answer 22

Remaining granulosa and the a interna cells that develop into lute in cells

Secrete oestrogen and progesterone to prepare uterine mucosa for implantation

Question 23

How is the oocyte transported into and through the uterine tubes?

Answer 23

Fimbrae sweep over the ovary and guide the ovum in.

Uterine tube contracts rhythmically to propel the ovum

Question 24

What is the corpus albicans?

Answer 24

Degeneration of the corpus luteum forming scar tissue. Precipitates menstrual bleeding