REPRODUCTIVE SYSTEM

Question 1

Explain the layers of the uterus

Answer 1

Perimetrium

Myometrium: muscular layer

Endometrium: mucosal inner layer, 2 part

• Strata functionalists: changes in response to ovarian hormones, undergoes menstruation
• Strata basialis: un response to ovarian hormones

Question 2

Define the ovarian cycle and its phases

Answer 2

series of changes where a follicle and ovum mature.

Follicular phase: ovulation occurs

Luteal phase: period of corpus lute activity

Question 3

Explain the steps of the ovarian cycle regarding follicle growth

Answer 3

Primordial follicle: oocyte surrounded by granulosa cells

Primary follicle activated at puberty: cells become cuboidal, zone pellucida forms and oocyte fully grown

Preantral phase: Granulosa cells proliferate and form layers of early theca (produce oestrogen).

Early astral follicle: Antrum starts to form

Question 4

Explain the dominant follicle formation

Answer 4

1-25 of the preantral follicles continue to develop

only one dominant follicle.

The non dominant follicles undergo atresia (apoptosis) at any stage of follicular growth.

Question 5

Explain the physical process of ovulation

Answer 5

Mature follicle has a large antrum where the oocyte projects into cavity.

Ballooning of follicle walls cause ovary to rupture

Lutenising hormone allow ovulation to occur

Left over follicle closes around antrum and granulosa cells enlarge

Granulosa + internal theca cells form corpus luteum

Question 6

What happens to the corpus luteum

Answer 6

Secretes progesterone and some oestrogen until the placenta can take over

If the egg is not fertilised the corpus lute degenerates into the corpus albicans (a scar)

Question 7

Explain the hormone levels during the ovarian cycle

Answer 7

FSH: early part of follicular phase

LH: Spike 18 hours before ovulation

Estrogen: Increases as dominant follicle grows. second peak due to corpus luteum

Progesterone: Low until just before ovulation. Increases after due to corpus luteum

Inhibin B: inverse to FSH in follicular phase as produced by earlier follicles

Inhibin A: Produced by older follicles to stop FSH secretion

Question 8

Explain the function of GnRH in the ovarian cycle

Answer 8

released by hypothalamus to cause FSH and LH release from anterior pituitary

FSH acts on granulosa cells

LH acts on theca cells

Question 9

Explain the functions of the LH surge

Answer 9

Causing primary oocyte to complete first meiotic division

Antrum size and blood flow to follicle increases

Granulosa cells produce enzymes that break the follicular-ovarian membrane for release

Transforms ruptured follicle into the corpus luteum

Question 10

Explain the menstrual phase

Answer 10

Day 1-5: menses

Estrogen and progesterone are low because corpus luteum is degrading

• endometrial lining sloughs
• secretion of FSH and LH is released to cause follicles to mature

Question 11

Explain the proliferative phase

Answer 11

Day 6-14: Prevovulatory

Proliferation of glandular epithelial cells, stroma and blood vessels with enlargement of glands to rebuild endometrium

Thins mucus to allow sperm into uterus at ovulation

Ovulation occurs at end of this phase

Question 12

Explain the secretory phase

Answer 12

Day 15-28: Postovulatory

Progesterone rises rapidly to prepare for implantation

Glands and stroma enlarge, arteries elongate and glycogen is secreted

Progesterone stops mutometrium contraction

If fertilisation does not occur luteum degenerates and menses phase begins

Question 13

What are the bodies response to oestrogen rising in puberty

Answer 13

Growth of ovary and early follicle

Increased genitalia, breast and bone growth (Ca uptake)

Widening and lightening of pelvis (feminisation)

Na reabsorption in renal tubule

Female libido

Question 14

What are the main functions of progesterone

Answer 14

Promotes secretory phase

Stimulates mucus production

decrease fallopian tube and myometrium contraction

-ve feedback reduces FSH and LH

Question 15

What are the main functions of androgens

Answer 15

Stimulate pubic hair and axillary hair growth

Maintains sex drive

Stimulate skeletal muscle growth

Question 16

How is an erection caused

Answer 16

Parasympathetic release of NO

relaxes smooth muscle so vessels dilate

Vascular channels enlarge with blood causing erection

Question 17

Explain the steps of spermatogenesis

Answer 17

Stem cells in basal compartment undergo mitosis to produce 2 1º spermatocytes

Move into adluminal compartment and undergo first meiotic division to form 2 2º spermatocytes

Second meiotic division to form 4 spermatids

Spermatids undergo spermiogenesis into spermatozoa

Question 18

How is the blood testes barrier maintained

Answer 18

As the 1º spermatocyte moves into the adluminal compartment tight junctions in front degrade and new junctions form behind them

Question 19

Explain spermiogenesis

Answer 19

Golgi packing acrosomal enzymes into acrosome

MTs elongate to form the flagellum

Mitochondria multiply and move to surround inner part of flagellum

Sperm released into lumen and matures in epididymis.

Question 20

Explain the function of GnRH in males

Answer 20

Secreted from hypothalamus once every 90 minutes to cause release of FSH and LH from anterior pituitary

LH acts on Leydig cells causing testosterone synthesis

FSH acts on sertoli cells to stimulate secretion of paracrine factors like ABP which bind to testosterone to keep concentration high and stimulate spermiogenesis

Testosterone -ve feedback stops GnRH and LH release and Inhibin from sertoli cells stops FSH release

Question 21

What are the other body functions of testosterone

Answer 21

Spermatogenesis (via sertoli cells)

Male accessory organs and secondary sex characteristics

Stimulates protein anabolism, bone growth, erythroprotein in kidneys

Question 22

Explain the travel of the effects through the fallopian tube

Answer 22

Fimbriae sweep oocyte into fallopian tube

Beating cilia move egg along fallopian tube

Takes 4 days to reach uterus

Question 23

Why do only 1000 sperm reach the fallopian tube

Answer 23

leaking from vagina

Acidic vaginal environment

Energy requirements for trip

Question 24

Explain capacitation

Answer 24

Changes in the sperms membrane so that it is fragile and acrosomal enzymes can be released

epididymis: membrane coated with proteins and cholesterol to keep tough
ejaculation: additional seminal plasma proteins to strengthen

Secretions of female tract cause capacitation

Question 25

Explain the steps of fertilisation

Answer 25

1. Sperm cell weaves past cumulus granulosa cells by hyaluronidase enzymes
2. Sperms binds to ZP3 of zona pellucida causing Ca release and acrosomal reaction
3. Acrosomal enzymes digest holes to get into oocyte
4. Sperm forms acrosomal process that binds to oocytes sperm binding receptors
5. Sperm and oocyte membranes fuse blowing contents inside
6. Entry of sperm contents causes rise of Ca triggering cortical reaction
7. Cortical reaction hardens zone pellucida and clips of sperm receptors to prevent polyspermy
8. oocyte completes meiosis II forming ovum and second polar body
9. Sperm and ovum nuclei swell forming pronuclei
10. Pronuclei approach each other and mitotic spindle forms between them
11. Chromosomes mix and DNA replicates for first cleavage division

Question 26

Explain the process of implantation

Answer 26

Integrin and selectin proteins on trophoblast cells bind to ECM of endometrial cells

If endometrium is not mature, blastocyst floats to lower level and tries again

Trophoblast cells proliferate and secrete enzymes to degrade endometrial tissue and bury into the layer

Question 27

What are some reasons that can cause implantation failure

Answer 27

scarring of uterus

Hormonal imbalance

Non-receptive endometriun

Ectopic pregnancy

Placent praevia (placenta may covering opening to vagina)

Question 28

What is placentation and describe the anatomy of the placenta

Answer 28

interlocking of foetal and maternal tissues

Chorionic villi extend into endometrium and contain blood vessels more nutrient exchange

Question 29

What are the functions of the placenta

Answer 29

Provides substrates for foetal metabolism

Disposes waste

Exchange of gases

Immune barrie

Produces pregnancy hormones

Question 30

What is the placenta impermeable and permeable to

Answer 30

Impermeable: large proteins and blood cells

Permeable: drugs and some pathogens

Question 31

What is the amniotic cavity and what are its functions

Answer 31

Forms between ICM and chorion, filled with amniotic fluid

Cushions foetus

Prevents uterus compression

Maintains temperatures

Fluid reservoir that foetus swallows

Question 32

Explain the production and functioning of pregnancy hormones

Answer 32

hCG produced by trophoblast cells at implantation to maintain corpus luteum and steroid production

Estrogen from trophoblast cells cause growth of uterine muscles

Progesterone from trophoblast cells inhibits uterine contractility

Question 33

What are the anatomic changes associated with pregnancy

Answer 33

Female organs become vascular due to estrogen and progesterone

uterus expands causing thorax to widen

lordosis

placental relaxation (pelvis widening for birth passage)

weight gain

Question 34

What are the metabolic changes associated with pregnancy

Answer 34

Human placental lactogen (hPL): matures breasts for lactation, stimulates glucose production in liver

Human chorionic thyrotropin (hCT): increases metabolism, parathyroid hormone and vitamin D causing bone turnover

Question 35

What are the physiological changes associated with pregnancy

Answer 35

Cardiovascular: blood volume, pressure and CO increase. Tachycardia

Respiratory: Tidal volume increases

GI: Morning sickness due to hormones, constipation

Urinary: Higher urine production due to higher metabolic rate

Question 36

What is preeclampsia

Answer 36

Symptoms: edema, protein in urine and hypertension

Causes decreased growth rate or death of foetus

Caused by abnormal vasoconstriction and inadequate implantation resulting in poor blood perfusion of placenta