Pregnancy and Lactation

Question 1

What is fertilisation?

Answer 1

A: The union of male and female gametes.
where? occurs in the oviduct, specifically in the ampulla (upper third of the oviduct).

Question 2

Describe the process of ovulation and the transport of the ovum to the oviduct.

Answer 2

During ovulation, the ova (egg) is released from the ovary into the abdominal cavity.
The ovum is quickly collected by the oviduct (fallopian tube).
The end of the oviduct has finger-like projections called fimbriae that cup the ovary and contract to sweep the ovum into the oviduct.
The oviduct is lined with cilia, which are tiny hair-like structures that help move the ovum towards the uterus.
The ovum is propelled through the oviduct by peristaltic contractions (wave-like muscle movements) and ciliary action.
The optimal site for fertilization is the ampulla region of the oviduct, where the sperm and ovum typically meet.

Question 3

Conception Process

Answer 3

During conception, several key factors play roles:
- Cervical Mucus: Normally thick, becomes watery during high estrogen levels, enabling sperm penetration.
- Ovum Release: Upon ovulation, the ovum releases progesterone, attracting sperm.
- Fertilization Site: Optimal in the ampulla of the oviduct.
- Limited Time Span: Conception window is short; if unfertilized 12-24 hours post-ovulation, the ovum disintegrates.
- Sperm Survival: Sperm typically survive around 48 hours but can persist up to 5 days in the female reproductive tract.
- Anatomy Involved: Uterus, ovary, oviduct, cervix, vagina, penis.
- Sperm Deposition: Roughly 180 million sperm are deposited during ejaculation.

Question 4

Fertilization Process:

Answer 4

Nuclei Fusion: Egg and sperm nuclei fuse to form a zygote.

Barriers Penetration: Sperm must pass through the corona radiata (a layer of cells that surrounds the ovum (egg cell) and zona pellucida.

Acrosomal Enzymes: Enzymes in the sperm head are released upon contact with the corona radiata, enabling the sperm to tunnel into the ovum.

Fusion with Ovum: The first sperm to reach the ovum fuses with its plasma membrane, triggering a chemical change that makes the membrane impenetrable to further sperm entry, preventing polyspermy.

Question 5

Key stages in the development process from fertilization to implantation.

Answer 5

1. Zygote stays in the ampulla (section in the fallopian tube) for 3-4 days.
2. During this time, it undergoes a series of mitotic divisions, forming a morula.
3. The corpus luteum produces progesterone, providing energy by stimulating the release of glycogen from the endometrium.
4. Forms the blastocyst with inncer cell mass and trophoblast. The inner cell mass is destined to become the fetus.
5. The trophoblast (outer layer of cells in the blastocyst) accomplishes implantation and develops into the fetal portions of the placenta.

Question 6

role of trophoblast

Answer 6

The trophoblast is the outer layer of cells in the blastocyst, which is the early stage of embryonic development. It forms shortly after fertilization and plays a crucial role in implantation and the subsequent development of the placenta. The trophoblast is responsible for adhering to the uterine wall during implantation, facilitating the exchange of nutrients and waste between the embryo and the mother, and eventually giving rise to the chorion, which contributes to the formation of the placenta.

Question 7

Key stages in the implantation process.

Answer 7

1. The blastocyst makes contact with the endometrial lining using the trophoblast cells.
2. Cords of trophoblastic cells begin to penetrate into the endometrium.
3. Trophoblastic cells release protein-digesting enzymes
4. An advancing cord of trophoblastic cells burrows deeper into the decidua, creating a hole for the blastocyst.
5. When implanatation is finished, the blastocyst is completely buried in the endometrium
6. Endometrial cells secrete prostaglandins, locally increasing vascularization, edema, and enhancing nutrient storage.

• Trophoblastic Activity: The trophoblastic layer continues to digest surrounding cells, providing energy to the embryo until the placenta forms.

Trophoblasts accomplish two critical actions:
Implantation: Carving a hole for the blastocyst.
Producing metabolic fuel for the developing embryo.

Question 8

whats decidua

Answer 8

• Decidua Formation: Decidua refers to the endometrial tissue at the site of implantation, crucial for supporting embryonic development.

Question 9

Key stages in the interaction between the developing embryo and maternal blood. a)
formation of chorionic villi

Answer 9

chorionic villi = Chorionic villi are finger-like projections that form the fetal portion of the placenta.

1. Syncytiotrophoblast (ST) ( a layer of cells derived from the trophoblast) extends into decidua:
   Embryonic cells migrate into the syncytiotrophoblast (ST), forming a multi-nucleated mass.
2. Lacunae (small cavities in the syncytiotrophoblas) in ST develop into extensions of maternal arteries.
3. Cytotrophoblast (a layer of cells derived from the trophoblast) forms primary villi, which penetrate the syncytiotrophoblast (ST) to become chorionic villi.
   C. Foetal blood vessels grow into chorionic villi.
   D. Cytotrophoblast chorionic villi and shell form:
   Anchoring (which attach the placenta to the uterine wall) and branch villi create a surface in the intervillous space for nutrient exchange to occur across the membrane from mother to embryonic vessels.

Question 10

prostaglandins

Answer 10

basically promotes vascularisation
1. endometrial cells secrete prostaglandins during implantation
–> locally increase vascularisation,
oedema and enhance nutrient
storage
2. endometrial cells secrete prostaglandins, particularly during the menstrual cycle and pregnancy.
–> involved in the contraction of the uterus, leading to the shedding of the endometrial lining during menstruation
3. during pregnancy, prostaglandins help to increase blood flow to the uterus, promote cervical ripening, and initiate labor.
4. In males, prostaglandins are found in semen and are released by the prostate gland. They play a role in several aspects of male reproductive physiology, including sperm motility, uterine contractions to aid sperm movement towards the fallopian tubes, and facilitating fertilization.

Question 11

Key stages in the interaction between the developing embryo and maternal blood.

Answer 11

corpeus leutem degenerates as placenta produces hormones
The placenta produces hormones, while the chorionic villi (part of the placenta) contain embryonic blood vessels.
Maternal blood bathes the chorionic villi, facilitating exchange of nutrients and waste products.
Extraembryonic membranes (chorion and amnion) enclose the embryo.

umbilical vein (carrying well-oxygenated blood to the embryo) and umbilical arteries (returning embryonic blood to the placenta).

Question 12

The Placenta – an endocrine gland

Answer 12

secretes hormones that maintain pregnancy such as

• Human chorionic gonadotropin (hCG): Secreted to prolong the life of the corpus luteum, which produces estrogen and progesterone, sustaining pregnancy until the placenta takes over.
• Estrogen and Progesterone: Secreted at increasing levels during pregnancy to maintain a thick endometrial layer and halt menstruation, crucial for supporting fetal development.

Question 13

Q: What are the stages of labor?

Answer 13

water breaks : At the onset of labour, or sometimes during first stage, the amniotic sac ruptures
* helps lubricate the birth canal
* Volume of fluid depends on position of placenta and baby

1. Cervical Dilation: The cervix gradually opens (dilates) to allow the baby to pass through the birth canal.
2. Delivery of the Baby: Uterine contractions increas in strength=>The baby is pushed through the birth canal and delivered.
3. Delivery of the Placenta: After the baby is born, the placenta is expelled from the uterus.

Question 14

What are the stages of labor and their key characteristics?

Answer 14

1. Cervical Dilation:
   Longest stage, lasting several hours to 24 hours.
   Contractions begin, gradually opening the cervix to accommodate the baby’s head.
2. Delivery of Baby:
   Begins when cervical dilation is complete.
   Typically lasts 30 to 90 minutes.
   Fetus drops lower in uterus causes cervical stretch
   Stretch receptors in the vagina trigger contractions of the abdominal wall to aid delivery.
   oxytocin from posterior pituitary stimulates prostaglandins from uterine wall to promote uterine contractions, which positve feedback to cause more cervical stretch
3. Delivery of Placenta:
   Occurs after the baby is born.
   Second series of contractions separate the placenta from the uterus and expel it through the vagina.
   Shortest stage, usually completed within 15 to 30 minutes.
   Continued uterine contractions prevent hemorrhage and aid in the uterus to shrinks to pre-gestational size (involution), returning the uterus to its pre-pregnancy size over 4-6 weeks.
   placenta is expells

Question 15

Q: What are the key points about lactation?

Answer 15

1. Elevated levels of placental estrogen and progesterone during pregnancy promote mammary gland development. == During pregnancy, hormones from the placenta help boobs get ready for milk-making

When the baby’s born, those hormones take a break, which tells your body it’s time to start producing milk. == Withdrawal of these hormones at childbirth initiates lactation.
The first milk (the initial milk produced by the breasts during the first few days after giving birth), colostrum, is highly concentrated and boosts early immunity.
Breastfeeding is super beneficial for babies. It’s recommended by WHO to breastfeed until 2 years or even longer, starting with only breast milk for the first 6 months.
Plus, breastfeeding can help prevent getting pregnant again too soon since it keeps hormones in check.

Question 16

colostrum

Answer 16

“First milk,” also known as colostrum, is the initial milk produced by the breasts during the first few days after giving birth.
Colostrum is thick and yellowish and contains high concentrations of antibodies, proteins, vitamins, and minerals.
It serves as a baby’s first food and provides essential nutrients and immune factors crucial for their early growth and protection against infections.
Colostrum acts as a natural vaccine, helping to build the baby’s immune system and protect them from illness.

Question 17

Hormonal control of lactation

Answer 17

1. Hormonal Control of Lactation:
   
   • The process of lactation (milk production) is regulated by hormones.
   • Two key hormones involved are prolactin and oxytocin.
2. Prolactin:
   
   • Source: Produced by the anterior pituitary gland.
   • Function:
     
     • Prolactin stimulates milk production in the mammary glands.
     • It blocks the release of PIH (prolactin-inhibiting hormone), allowing milk synthesis.
   • Role in Lactation:
     
     • Prolactin levels increase during pregnancy and remain elevated after childbirth.
     • It promotes milk production and maintenance.
3. Oxytocin:
   
   • Source: Produced by the hypothalamus and released from the posterior pituitary gland.
   • Function:
     
     • Oxytocin triggers uterine contractions during labor.
     • It also plays a crucial role in the milk ejection reflex (let-down reflex).
   • Role in Lactation:
     
     • When a baby suckles at the breast, oxytocin is released.
     • It causes myoepithelial cells around the alveoli (milk-producing structures) to contract.
     • This contraction moves milk into the ducts, facilitating breastfeeding.
4. Feedback Inhibitor of Lactation (FIL):
   
   • Local Regulation:
     
     • FIL is present in breast milk.
     • It limits milk production locally by inhibiting further milk synthesis.
     • This ensures a balance between milk supply and demand.

Question 18

Q: What is the Feedback Inhibitor of Lactation (FIL) and how does it work?

Answer 18

Local Regulation:
FIL is a protein naturally present in breast milk.
Its job is to control milk production right where it’s needed, in the boobs.
When there’s enough milk, FIL steps in to tell the boobs to slow down production, preventing overproduction.
This keeps a perfect balance between how much milk is made and how much the baby needs.

Question 19

Q: How does lactation affect the skeleton, and what is its link to bone health?

Answer 19

During lactation, the body prioritizes the production of breast milk to nourish the baby ==> breaks down bone to produce breast milk.

Since breast milk requires calcium for its composition, the body uses various mechanisms to ensure an adequate supply of calcium for milk production, one of which involves breaking down bone tissue to release calcium into the bloodstream.

While this can lead to temporary bone loss in lactating women, the body usually replenishes the lost bone mass after breastfeeding ends.

Bone Loss during Lactation:
Women can lose 5-10% of trabecular bone mass (the spongy part of bones) during lactation.

Source of Calcium:
Bones act as a source of calcium for breast milk production during lactation.

Increased Bone Breakdown:
Osteoclasts, cells that break down bone tissue, become more active during lactation, leading to a process called osteocytic osteolysis where calcium is released from bones into the blood.

Risk of Osteoporosis:
Although rare, excessive bone loss during lactation can potentially lead to osteoporosis (weak and brittle bones) and fractures in some cases.

Question 20

contraception

Answer 20

1. Surgical or Implants (99% effective):
   
   • Implant: A small rod inserted under the skin that releases hormones to prevent pregnancy.
   • IUD (Intrauterine Device): A T-shaped device placed in the uterus to prevent fertilization.
   • Surgical Sterilization: Permanent methods like tubal ligation (for females) or vasectomy (for males).
2. Hormonal/Steroids (92–97% effective):
   
   • Shot: Injectable contraceptive containing hormones.
   • Ring: A flexible ring inserted into the vagina, releasing hormones.
   • Patch: Hormone-releasing patch applied to the skin.
   • Pills: Oral contraceptive pills containing hormones.
3. Barrier (78–82% effective):
   
   • Male/Female Condoms: Physical barriers preventing sperm from reaching the egg.
   • Diaphragm: A dome-shaped device placed over the cervix.
   • Sponge: A soft, spermicide-coated barrier.
4. Natural (71–76% effective):
   
   • Calendar Methods: Tracking fertile days based on menstrual cycle.
   • Spermicide: Chemicals that kill sperm.
   • Withdrawal Method: Withdrawal before ejaculation.