Lectures 26 & 27: Embryology, Pregnancy And Childbirth Flashcards
Fertilisation
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
What do each of these mean? Pregnancy? Conceptus Gestation period Conception day? Fertilisation?
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.
Cleavage slide 6
Trophoblast tests readiness of endometrium for implantation and floats down until it finds a site that is ready!
Implantation slide 7
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.
Describe the hormonal profile of pregnancy
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
How is the placenta made?
Slide 9
Trophoblast cell layerchorion
Chorionic villi project from fetal tissue into maternal blood vessels. Form umbilical arteries and vein.
Placenta= chorionic villi + decidua basalis
Slide 10
Umbilical vein carries?
Umbilical artery carries?
Umbilical vein: oxygenated blood➡ mother➡ placenta➡ fetus
Umbilical artery: deoxygenated blood + waste ➡ fetus➡ placenta➡ mother
Mesodermal differentiation
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.
Forgut = epigastric
What are the adult derivatives?
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).
Midgut= umbilical
Adult derivatives?
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.
Hindgut= hypogastric
Adult derivatives?
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.
Tell me about the embryo logical development of the pancreas?
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.
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?
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.
Liver development?
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.
Now for fetal development! Month by month
First month
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.
Second month
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.
Third month
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.
Fourth month
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.
Fifth month
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.
Six months
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.
Seven months
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
Eight months
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.
Nine months
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.
Know the shit out of this
Uterine changes during pregnancy
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
What are the effects of pregnancy on the pelvis?
Star
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
Aetiology of back pain in pregnancy
Know this
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.
Tell me about pregnancy and chiropractic
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.
How will the fetal head fit through the urogenital hiatus of the pelvic diaphragm?
Don’t know
Stages of birth
Stage 1: dilation
Stage 2: delivery of fetus
Stage 3: delivery of placenta
What are the circulatory changes in baby?
Slide 55
Yep
Postnatal involution of the uterus
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.
Lactation
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
What arises from each layers?
Ectoderm
Mesoderm
Endoderm
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.
