12. Reproductive System Flashcards
1
Q
Reproduction
A
- Reproduction describes the production of new offspring.
- ‘Sexual reproduction’ involved meiosis & fertilisation.
- Meiosis produces male (sperm) and female (ova) gametes, which are haploid (23 chromosomes).
- The offspring has a mix of genes inherited from each parent (produces genetic variability).
- Fertilisationproduces a‘zygote’, which contains 46 chromosomes.
2
Q
Reproductive System: Functions, Female
A
- Formation of ova (female gametes).
- Reception of spermatozoa (male gametes).
- Provide suitable environment for fertilisation/foetus.
- Parturition (childbirth).
- Lactation.
3
Q
Reproductive System: Functions, Male
A
- Production of spermatozoa (male gametes).
2. Transmission of spermatozoa to the female.
4
Q
Breasts/Mammary glands
A
- The breasts are accessory glands of the female reproductive system.
- Within each breast is a mammary gland –a modified sweat gland producing milk.
- Each mammary gland consists of 15-20 lobes, separated by adipose tissue. Lobes contain small grapelike clusters of glands called alveoli.
- ‘Suspensory ligaments’ support the breast between the skin & underlying fascia.
5
Q
Lactation:
A
- Contraction of myoepithelial cells surrounding alveoli help propel milk into lactiferous ducts.
- Milk can be stored in lactiferous sinuses.
- After birth, the hormone ‘prolactin’stimulates milk synthesis, whilst ‘suckling’ stimulates ‘oxytocin’,which causes milk ejection.
6
Q
Uterus
A
The uterus serves as a pathway for sperm, the site of zygote implantation and location for foetal development. The uterus contractsto initiate labour.
7
Q
Uterus: Tissue layers
A
- Perimetrium: Outer layer (visceral peritoneum).
- Myometrium: Three smooth muscle layers.
- Endometrium: The highly vascular inner layer that is divided into the‘stratum functionalis’ (sloughs off during menses) &‘stratum basalis’, which is the permanent deeper layer that regenerates the stratum functionalis.
8
Q
Uterus: Structure
A
• The uterus consists of the fundus, body and cervix.
• The uterus is held in place by ligaments such as the
‘broad ligament’.
• The cervix is the narrowed inferior portion of the uterus that leads into the vagina.
• The uterus is situated between the bladder
(anteriorly) and rectum (posteriorly); it is the size &
shape of an inverted pear.
9
Q
Endometrium
A
- The endometrium is the highly vascularised inner layer of the uterus.
- During a ‘period’ (“menses”), the stratum functionalis sheds, leaving behind the stratum basalis.
- After shedding, the endometrium re-builds to prepare for implantation of a fertilised egg.
- If the egg is fertilised, the zygote is embedded in the endometrium.
- In the first 8 weeks, the embedded zygote is an embryo.
- After 8 weeks, the embryo becomes a foetus.
10
Q
Placenta
A
- The placenta is the site of exchange of nutrients and wastes between the mother and foetus, attached to the endometrium.
- The placenta also produces hormones that are needed to maintain the pregnancy.
- By the beginning of the twelfth week, the placenta contains two distinct regions.
- The placenta is unique because it develops from two individuals (maternal part from endometrium).
- The actual connection between the placenta and embryo/foetus is through the umbilical cord, which is 50–60cm in length.
- The placenta allows oxygen and nutrients to diffuse from maternal blood into foetal blood, whilst carbon dioxide and wastes move in the opposite direction.
- Provides a protective barrier because most micro-organisms cannot pass through it. Some organisms such as HIV, measles and polio can. Alcohol and many drugs can pass freely and can cause birth defects.
- Blood cellscannotcross the placenta.
- Nutrient transfer to the foetus is mediated by proteins called nutrient transporters.
11
Q
Placental Hormones
A
Progesterone Oestrogen human Chorionic Gonadotrpin (hCG) human PlacentalLactogen (hPL) Relaxin Corticotropin releasing hormone (CRH)
12
Q
Progesterone
A
- Maintains endometrial liningto sustain and nourish the foetus.
- Produced by corpus luteum until 8 weeks.
13
Q
Oestrogen
A
- Promotes growth of breast tissueand myometrium.
* Produced by corpus luteumuntil 8 weeks.
14
Q
human Chorionic Gonadotrpin (hCG)
A
- Only produced during pregnancy(test!)
- Maintains corpus luteum for 8 weeks and increases transfer of nutrients to foetus.
- Related to morning sickness.
15
Q
human PlacentalLactogen (hPL)
A
Increase the amount of glucose & lipids in maternal blood.
16
Q
Relaxin
A
- Targets ligamentsand relaxes them.
* Produced by the corpus luteum and placenta.
17
Q
Corticotropin releasing hormone (CRH)
A
- Triggers release of cortisolfrom the adrenals.
* Prevents rejection of foetus / placenta.
18
Q
Placenta Praevia
A
- Occurs when the placenta attaches to the lower part of the uterine wall, potentially occluding the opening of the cervix.
- Risk with multiple births because more placentas.
- 1st trimester can resolve itself as uterus stretches.
- 2nd or 3rd trimester (>20 weeks) prone to haemorrhage. Wall of cervix stretches and can detach from the placenta. Uterine vessels rupture and often presents as painless, ante-partum vaginal bleeding.
- Treatment depends on the condition of the baby and mother. C-section preferred.
19
Q
Placenta Accreta
A
- Abnormally deep attachment of the placenta through the endometrium into the myometrium.
- If invades myometrium = increta. If through uterine wall to viscera such as the bladder = percreta.
- Due to inadequate (thin) basalis layer of endometrium. The placenta has to “dig in deeper” when implanting.
- Occurs due to: C-section, curettage (scraping procedure), fibroid removal or placenta praevia.
- Risk of post-partum haemorrhage.
20
Q
Placental Abruption
A
- Rupture of blood vessels adhering the placenta to the uterine wall leading to separation of the placenta from the uterus.
- Risk factors include smoking & maternal hypertension (pre-eclampsia).
- Presents as abdominal pain and ante-partum bleeding.
- An obstetric emergency after 20 weeks:
- > 30 weeks: delivery.
- <30 weeks and stable vitals monitor until baby is old enough to safely deliver. Mature foetal lungs with corticosteroids.
- Occurs in 1% of pregnancies worldwide.
21
Q
Twins: Monozygotic (30%)
A
- Identical twins (same genetic information).
- Originate from a single fertilised ovum (One egg, one sperm).
- The zygote splits into 2 embryos, but share 1 placenta.
22
Q
Twins: Dizygotic (70%)
A
- Non-identical.
- Release of two ova and fertilisation of each. Implanted independently.
- Two eggs, two sperms
- Two different placentas.
23
Q
Fallopian Tubes
A
- The fallopian (or uterine) tubes extend laterally from the uterus (~10cm tubes).
- The tubes provide a route for the sperm to meet the ova and for the ova (or fertilised ova) to reach the uterus.
- Finger-like projections calledfimbriae surround the ovary and ‘sweep the ova’ into the fallopian tube.
- The tubes are lined with ciliated columnar epithelium, which function to help move the ova towards the uterus.
- The smooth muscle layer performs peristalsis to assist in ova movement.
24
Q
Ovaries
A
- The ovaries are the female gonads and exist as paired glands.
- The ovaries resemble almondsin their shape and size, although atrophy after menopause.
- The ovarian ligament anchors the ovaries to the uterus, whilst the broad ligament also assists in maintaining the position of the ovaries.
- The ovaries produce female gametes (‘secondary oocytes’ via oogenesis).
- Ovaries secrete sex hormones: oestrogen & progesterone.
