Reproduction, Development and Ageing Flashcards
What is the conceptus?
Everything produced from the fertilized egg
What causes regulation of cells during proliferation and differentiation of the developing foetus?
Paracrine and autocrine effect of hormones
How long is a normal pregnancy?
37-41 weeks
What is gastrulation? What is the result?
Formation of a 3-layer embryo Results in 3 germ layers - Ectoderm - Mesoderm - Endoderm
What is the fate of the different germ layers?
Endoderm: gut, liver, lungs Mesoderm: Skeleton, muscle, kidney, heart, blood Ectoderm: skin, nervous system
How is the CNS formed during neurulation?
Formed from the ectoderm Neural groove does not undergo differentiation. Cells move and fuse to form the CNS
When does closure of the body cavity occur?
Begins at 21 days Closes around 28 days
What development occurs in the second month PF?
- Limbs develop days 28-56 - Face develops - Internal tissues develop (heart and lungs, gut) - Looks like a foetus by day 56
What is the difference between PF and GA
Gestational age: Measured from day of last period Post-fertilisation: Fertilisation occurs 2 weeks after the last day of period
What causes spina bifida?
When there is failure to complete neurulation; formation of a posterior neuropore - Usually occurs towards the bottom of the spine - Contents and location determines the outcome - Vertebrae do not form correctly about the maformation. Neural tissue directs bone formation Incidence: 1-2 per 1000 pregnancies Surgery can hep anatomical but not functional problems
What are the different types of spina bifida?
Spina bifida occulta: Vertebrae do not form correctly. Superficially there are hairs above that part of the spine Spina bifida meningocele: Pocket of CSF Spina bifida myelomeningocele: More severe; part of the neural cord contained within the pocket
What is the incidence of anencephaly?
1-8 per 10,000 births Female > male
How does the heart develop in utero?
- Heart tubes are at the greater edge of the blastocyst. - Greater fold pushes heart tubes underneath and towards the cranial edge of the embryo - The two heart tubes fuse to form the primitive heart tube - Primitive atrium rotates around the primitive ventricle, whilst the primitive ventricle grows in size, until the atrium is sat behind the ventricle - New connection forms between right atrium and ventricle
What is the ductus arteriosus?
Connection between aorta and pulmonary artery allows blood to bypass the lungs until birth
What changes occur to the heart after birth?
Before - Deoxygenated blood from the upper body and oxygenated blood from the placenta enter the right atrium - Goes to right ventricle - Minimal blood goes to the lungs and most goes through the ductus arteriosus into the aorta - Small amount of blood returns from lungs into right atrium, into ventricle then into the aorta After - Blood into right atrium is no longer a mix of oxygenated and deoxygenated, as no oxygen from placenta - Ductus arteriosus closes so all blood from right ventricle goes to the lungs
How do the limbs develop?
- Forelimb bud appears at day 27/28 - Hindlimb bud appears at day 29 - Grow out from lateral plate mesoderm rapidly under control of special signalling regions - Fully formed and patterned by day 56
What causes acondroplasia?
Gain of function mutation in FGFR3
What is Thalidomide? What effect does it have on foetal development?
- A drug used ~1958-1962 to treat morning sickness - Currently used to treat leprosy and cancer - Typically caused poor development of upper limbs - In addition caused deformed eyes and heart, deformed alimentary and urinary tracts, blindness and deafness - Interferes with blood vessel development (Morning sickness peaks at 8 weeks- same time as limb development)
What is polydactyly?
Malformation of the hand causing 5 fingers and a thumb. Cells direct development of each digit, extra cell present No functional problems
How do the kidneys develop in utero?
Pronephros develops first. Precursor tissue that directs formation of the Mesonephros which connects to the cloaca. There are limited excretory functions. Early fourth week: Uretetic bud appears Sixth week: Metanephric blastema (metanephros = definitive kidney) Eighth week: Differentiating metanephric tissue ascends
How do the kidneys ascend?
- The kidneys initially formed near the tail end of the embryo - Vascular buds from the kidneys grow toward and invade the common iliac arteries - Kidney position changes relative to: a) adrenal glands b) gonads - Rather than “drag” their blood supply with them as they ascend, the kidneys send out new and slightly more cranial branches and then induce the regression of the more caudal branches
What does the bladder develop from in utero?
Mostly endodermal, except the trigone (mesodermal) which develops from the mesonephric duct (Trigone signals filling of the bladder to the brain)
What are the possible outcomes if development of the kidneys goes wrong?
- Renal agenesis - Abnormal shaped kidneys - Abnormal ureter - Pelvic or horseshoe-shaped kidneys - Bladder exstrophy
What causes renal agenesis?
- Early degeneration of ureteric bud - Unilateral renal agenesis 1:1000 L>R - Bilateral - Potter’s syndrome (oligohydramnios)