Endocrine System IV

Question 1

What are the stages of reproduction?

Answer 1

Gametogenesis, fertilisation, implantation, pregnancy, parturition, lactation

Question 2

What is gametogenesis?

Answer 2

Gametes generation (meoisis) - Production of reproductive cells/gametes

Question 3

What is fertilisation?

Answer 3

Gametes fuse to produce new cell

Question 4

What is implantation?

Answer 4

6 days post fertilisation

Question 5

Briefly define pregnancy

Answer 5

Fetus development

Question 6

What is parturition?

Answer 6

Labour

Question 7

What are the primary reproductive organs?

Answer 7

Gonads - Testes in males, Ovaries in females

Question 8

What are the dual functions of the gonads?

Answer 8

Gametogenesis - Spermatozoon (zoa - sperm), Ovum (ova - female)
Secretion of steroid/sex hormones

Question 9

Describe sex hormones

Answer 9

Testes - Testosterone/androgen
Ovaries - Estrogens/Progesterone
Found in both m/f
Adrenal cortex produces androgen too

Question 10

What are gonadotropins?

Answer 10

Regulating hormones, same molecular structures in both sexes

Eg: FSH (follicle stimulation hormone) and LH (luteinising hormone) from the anterior pituitary

Question 11

Describe gonadotropins

Answer 11

Stimulated by GnRH (gonadotropin releasing hormone) from hypothalamus

Question 12

Describe what a cross-section of an area of testis would look like

Answer 12

Blood vessel, sperm, sertoli cells (sperms), lumen of seminiferous, leydig cells (intestitial cells - Hormone)

Question 13

Describe testosterone in the male

Answer 13

Needed for initiation/maintenance of spermatogenesis (via sertoli cells)
Induces differentiation of male accessory reproductive organs to maintain function
Induces male secondary sex characteristics

Question 14

Further describe testosterone in terms of RBCs

Answer 14

Stimulates protein anabolism, bone growth, and cessation of bone growth
Required for sex drive (can enhance aggressive behaviour
Increases RBC volume
Gives negative feedback to GnRH and LH secretion

Question 15

Describe the menstrual cycle in the uterine

Answer 15

Day 1-14 - Follicular phase
Day 14-28 - Luteal phase
Days 1-5 - Menstrual phase
Days 5-14 - Proliferative phase
Days 14-28 - Secretory phase

Question 16

Describe the structure of the menstrual cycle graph for the uterine

Answer 16

Menstruation, Endometrial gland, Blood vessels, Endometrial thickness

Question 17

What is the average number of days for a cycle?

Answer 17

25-35 days/cycle, average 28 days

Question 18

Describe the 2 stages of the menstrual cycle

Answer 18

Follicular (pre-ovulation) phase, concerned with maturing of follicle
Luteal (post-ovulation) phase - Consistently 14 days

Question 19

Describe the basic reproductive unit of the ovary

Answer 19

Oocyte surrounded by granulosa cells - Surrounding cells enlarge, after ovulation remain form the corpus luteum needed for hormonal secretion

Question 20

Describe the menstrual cycle under FSH stimulation

Answer 20

Many follicles increase rates of maturation

One becomes dominant

Question 21

Describe what happens during the menstrual cycle per day

Answer 21

1-5: Menstrual, endometrial sloughs
7: Dominant follicle selected
7-12: Plasma estrogen inc to endometrium proliferation
12-13: LH inc (+FB)
14: Ovulation (mediated by enzymes/prostaglandin)
15-25: Corpus luteum forms/secretes estrogen/progesterone, FSH/LH inhibited, no new follicles
25-28: Corpus luteum degenerates, estrogen/progest conc dec, endometrium starts to slough, new cycle begins

Question 22

Describe the development of a human oocyte and ovarian follicle

Answer 22

Primordial follicle, primary follicle, preantral follicle, early antral follicle, mature follicle

Question 23

Describe early embryonic development

Answer 23

Fertilisation - Zygote
Cleavage (total volume same) > Early cleavage (4 cell stage), Morula (3-4 days post-fertilisation)
Blastocytes (4-5 days)
Implantation (6 days)

Question 24

Describe hormonal changes in pregnancy in terms of HCG

Answer 24

Ovum fertilisation occurs, placenta secretes chorionic gonadotropin (HCG) into circulation, maintains corpus luteum, stimulates progesterone production
Placenta eventually becomes major source of progesterone/estrogen

Question 25

Describe hormonal changes in pregnancy in terms of progesterone and estrogen

Answer 25

Progesterone - LT maintenance of fetus, prevents uterine activity/premature expulsion of fetus
Estrogen - Stimulate continuous growth of uterine muscles necessary for labour

Question 26

Describe hormonal changes in pregnancy in terms of relaxin

Answer 26

Corpus luteum/placenta also secrete hormone relaxin which promotes softening of tissues to prepare for childbirth

Question 27

Describe the graph of hormonal changes in pregnancy

Answer 27

HCG only increases around 1 month, at the greatest urine excretion rate at 2 months, then plateau back at 3 months and stays constant till delivery
Estrogen and progesterone increase at similar rate gradual slope, estrogen greater and is high during delivery, progesterone is lower but needed for delivery, both plateau

Question 28

Describe the hormones in parturition

Answer 28

Drop in ratio of progesterone/estrogen causes uterus to be susceptible to contraction
Oxytocin from pituitary is a major stimulator of myometrial contraction

Question 29

Describe hormones in parturition in terms of prolactin

Answer 29

Milk production controlled by prolactin (inc during pregnancy)
Progesterone/estrogen inhibits milk production during pregnancy, stops after removal of placenta

Question 30

Describe hormones in parturition in terms of post-pregnancy

Answer 30

Upon sucking reflex prolactin released to stimulate mammary glands to produce milk
Oxytocin also released to cause smooth muscles to contract to expel milk
Prolactin inhibits GnRH (so FSH/LH too), difficult to get pregnant again initially