Lectures 26 & 27: Embryology, Pregnancy And Childbirth

Question 0

Fertilisation

Answer 0

Once a single sperm binds to oocyte plasma membrane a reaction occurs to exclude all others.
Sperm unpacks its baggage of 23 chromosomes and then migrates to centre.
Pronuclei membranes rupture next to mitotic spindle and chromosomes line up ready for first mitotic division.
Slide 5

Question 1

What do each of these mean?
Pregnancy?
Conceptus
Gestation period 
Conception day?
Fertilisation?

Answer 1

Pregnancy = Events that occur from conception until birth.

• Conceptus = “that which is conceived”
• Gestation period = (gestare = to carry) = Last menstrual period until birth (~ 280 days).
• So conception day = 2 weeks pregnant!
• Fertilisation  2 week conceptus = pre-embryonic period (2 – 4 weeks gestation)
• 3 – 8 weeks after fertilisation (5-10 weeks gestation) = embryo.
• 9 weeks to birth (11+ weeks gestation) = fetus.

Question 2

Cleavage slide 6

Answer 2

Trophoblast tests readiness of endometrium for implantation and floats down until it finds a site that is ready!

Question 3

Implantation slide 7

Answer 3

Blastocyst implants into endometrium by secreting digestive enzymes, cytokinds and growth factors onto the endometrial surface.
Takes about a week to complete implantation.
Trophoblast cells secrete human chorionic gonadotrophin which is measured in urine to test for pregnancy.

Question 4

Describe the hormonal profile of pregnancy

Answer 4

Trophoblast (and then chorion) cells secrete hCG.
hCG prompts corpus luteum to keep secreting progesterone until placenta takes over.
Placenta makes and secrete oestrogen and progesterone for remainder of pregnancy until birth.
Slide 8

Question 5

How is the placenta made?

Slide 9

Answer 5

Trophoblast cell layerchorion
Chorionic villi project from fetal tissue into maternal blood vessels. Form umbilical arteries and vein.

Placenta= chorionic villi + decidua basalis
Slide 10

Question 6

Umbilical vein carries?

Umbilical artery carries?

Answer 6

Umbilical vein: oxygenated blood➡ mother➡ placenta➡ fetus

Umbilical artery: deoxygenated blood + waste ➡ fetus➡ placenta➡ mother

Question 7

Mesodermal differentiation

Answer 7

Notochord
• Somites: sclerotome, dermatome, myotome.
• Intermediate mesoderm => gonads, kidneys, adrenal cortex.
• Lateral somatic mesoderm => dermis, peritoneum, limb buds.
• Lateral splanchnic mesoderm => cardiovascular system organs, connective tissues, all but epithelial lining of digestive and respiratory organs.

Question 8

Forgut = epigastric

What are the adult derivatives?

Answer 8

Adult derivates:
• Pharynx, tongue, tonsils, salivary glands, upper respiratory
system.
• Lower respiratory system.
• Oesophagus and stomach.
• Duodenum (proximal to common bile duct).
• Liver, gallbladder, bile duct system.
• Pancreas.
• Blood supply: coeliac artery (except pharynx, respiratory tract, most of oesophagus).

Question 9

Midgut= umbilical

Adult derivatives?

Answer 9

Adult derivatives:
• Small intestines (inc. most of duodenum)
• Caecum, vermiform appendix, ascending colon, right 1⁄2 - 2/3 of transverse colon.
• Blood supply:
superior mesenteric artery.

Question 10

Hindgut= hypogastric

Adult derivatives?

Answer 10

Adult derivatives:
• Small intestines (inc. most of duodenum)
• Caecum, vermiform appendix, ascending colon, right 1⁄2 - 2/3 of transverse colon.
• Blood supply:
superior mesenteric artery.

Question 11

Tell me about the embryo logical development of the pancreas?

Answer 11

4th week of development – ventral and dorsal buds from foregut.
• By the end of the 6th week, the rotation of the duodenum has brought ventral and dorsal buds together and they fuse.
• Ventral bud => head and uncinate process.
• Dorsal bud => Neck, body and tail.

Question 12

Embryo logical development
Primitive gut forms during 4th week?
Endoderm of primitive gut gives rise to?
Epithelium from cranial and caudal extremities is derived from the?
Muscular and connective tissue components of digestive tract are derived from the?

Answer 12

Primitive gut forms during 4th week.
• Endoderm of primitive gut gives rise to most of
the epithelium and glands of the digestive tract.
• Epithelium from cranial and caudal extremities is derived from the ectoderm of the stomodeum (primitive mouth) and proctodeum (anal pit).
• Muscular and connective tissue components of digestive tract are derived from the splanchnic mesenchyme surrounding primitive gut.

Question 13

Liver development?

Answer 13

Endoderm => hepatocytes, biliary epithelial cells
• Mesoderm => stromal cells, stellate cells,
kuppfer cells and blood vessels.
• Anterior portion of liver bud=> give rise to liver and intra-hepatic biliary tree.
• Posterior portion of liver bud=> gall bladder and extrahepatic bile ducts.

Question 14

Now for fetal development! Month by month

First month

Answer 14

By the end of the first month, the embryo is about 1/10 of an inch long. The heart, which is no larger than a poppy seed, has begun beating.

Question 15

Second month

Answer 15

By the end of the first month, the embryo is about 1/10 of an inch long. The heart, which is no larger than a poppy seed, has begun beating.

Question 16

Third month

Answer 16

By now the fetus is 2 1/2 to 3 inches long and is fully formed. He has begun swallowing and kicking. All organs and muscles have formed and are beginning to function.

Question 17

Fourth month

Answer 17

Your baby is covered with a layer of thick, downy hair called lanugo. His heartbeat can be heard clearly. This is when you may feel your baby’s first kick.

Question 18

Fifth month

Answer 18

A protective coating called vernix caseosa begins to form on baby’s skin. By the end of this month, your baby will be nearly 8 inches long and weigh almost a pound.

Question 19

Six months

Answer 19

Eyebrows and eyelids are visible. Your baby’s lungs are filled with amniotic fluid, and he has started breathing motions. If you talk or sing, he can hear you.

Question 20

Seven months

Answer 20

By the end of the seventh month, your baby weighs about 3 1/2 pounds and is about 12 inches long. His body is well-formed. Fingernails cover his fingertips

Question 21

Eight months

Answer 21

Your baby is gaining about half a pound per week, and layers of fat are piling on. He has probably turned head-down in preparation for birth. He weighs between 4 and 6 pounds.

Question 22

Nine months

Answer 22

Your baby is a hefty 6 to 9 pounds and measures between 19 and 22 inches. As he becomes more crowded, you may feel him move around less.

Question 23

Know the shit out of this

Uterine changes during pregnancy

Answer 23

By 4th month the uterus fills the pelvis.
By 9th month the fundus of the uterus is at the level of the xiphoid process.
Abdominal organs are pushed superiorly under the diaphragm

Question 24

What are the effects of pregnancy on the pelvis?

Star

Answer 24

Coccyx permitted to move more posteriorly to increase the pelvic outlet.
Conjugate distance between sacral promontory and posterosuperior aspect of pubic symphysis is fixed.
Transverse diameter & amount of pelvic rotation permitted around sacrum is increased due to effect of relaxin hormones on pelvic ligaments.
Slide 45

Question 25

Aetiology of back pain in pregnancy

Know this

Answer 25

Increased maternal weight  increases load on spine.
• Referred pain from visceral compression.
• Direct compression on exiting nerve roots in
pelvis.
• Venous congestion in pelvis and lumbar spine from uterus compression inferior vena cava.
• Relaxin hormone causing ligamentous laxity.
• Pelvic instability.

Question 26

Tell me about pregnancy and chiropractic

Answer 26

RCT study demonstrated that pregnant women receiving chiropractic care on a weekly basis from 24-33 weeks’ gestation had significantly lower self-rated pain and disability compared to those who received only standard obstetric care.
• Gentle joint mobilisation and trigger point release techniques were used.
• Improved range of motion, stability and less irritation of lumbar and pelvic joints of the pregnant women was observed by the Chiropractors at 33 weeks’ gestation compared to their baseline values from 24-28 weeks’ gestation.

Question 27

How will the fetal head fit through the urogenital hiatus of the pelvic diaphragm?

Answer 27

Don’t know

Question 28

Stages of birth

Answer 28

Stage 1: dilation
Stage 2: delivery of fetus
Stage 3: delivery of placenta

Question 29

What are the circulatory changes in baby?

Slide 55

Answer 29

Yep

Question 30

Postnatal involution of the uterus

Answer 30

The period when the mother’s body reverts to the typical non-pregnant state, morphologically and physiologically.
It has no sharp end but is conventionally regarded as lasting 6 weeks.
Involution of the uterus is rapid over first few days postpartum then tapers off until effectively back to quiescent state by 6 weeks; - pink immediately post delivery; blue at 5 days postpartum; black at 12 days postpartum.

Question 31

Lactation

Answer 31

True milk 2-3 days to come in.
• “Let-down” Reflex: oxytocin binds to myoepithelial cells surrounding alveoli ➡ milk ejected form alveoli into ducts from both breasts

Question 32

What arises from each layers?
Ectoderm
Mesoderm
Endoderm

Answer 32

Ectoderm➡ epidermis and nervous system
Mesoderm➡ smooth muscle, connective tissue, blood vessels, skeleton, skeletal muscle, reproductive and excretory organs
Endoderm➡ epithelial linings of respiratory passages and digestive tract.