Embryology Flashcards
Decent of testes facilitated by
- gubernaculum forms (guiding)
- testes enlarge (exert press of surroundings)
- mesonephros atrophies (makes room)
- paramesonephric ducts atrophy (makes room)
- processes vaginalis develops (creates path of low resistance though inhumanly canal)
- growth of penis, external genitalia and abdomen
Site of haematopoiesis in developing fetus
- wall of yolk sac
- spleen
- liver
- bone marrow
Undescended testes
Cryptorchidism
Septum transversum
Sheet of mesoderm that is pushed into place by the developing liver
- contributes to central tendon of diaphragm
- plays a role in the formation of the liver
Definition hypospadias
- abnormally placed urinary meatus anywhere along the urethral groove
- due to fault in folding if urethral folds
Development of indifferent gonad to testis
Based on genes of the sex-determining region on the short arm of the Y chromosome, medulla of indifferent gonad develops into testis
Features of tetralogy of Fallot
- VSD
- pulm stenosis
- over-riding aorta
- hypertrophy of RV
Description of foetal blood
- erythrocytes have a nucleus
- contain fetal Hb
- maternal and fetal blood usually do not mix
Haemolytic disease of the newborn
Immune problem from fetal rh+/ maternal rh-
- leaking of blood from fetus leads to maternal anti-rh antibodies
- problematic in future pregnancies
Blood development
- initially within core of blood islands in mesoderm (angioblasts)
- fuse and extend to make primordial vascular network
- 2 populations of cells in island:
- peripheral (form endothelial cells)
- core (form blood cells)
Summary of haematopoiesis.
- starts on day 19 in yolk sac (only erythrocytes with fetal Hb)
- at 5 weeks, embryo itself starts producing
- liver becomes chief site (beginning of leukocyte and thrombocyte prod)
- spleen, kidney, thymus and lymph nodes = minor sites
- BM is primary site from 6 months
Things that phenotypically differentiate the sexes
- gonads
- duct system
- external genitalia
- secondary sexual characteristics
Testis determining gene
SRY gene on Y chromosome
Sex germ cells
- in endoderm of yolk sac
- migrate go genital ridges (on ventromedial surfaces of mesonephric ridge)
- increase in no. as they migrate
Differentiation of the testis
- germ cells in mesonephric ridge form primitive sex cords
- sex cords become separated from surface epi by tunica albuginea
- outer portion = seminiferous tubules
- inner portion = rete testis
When do Sertoli cells start secreting MIS?
8 th week
Formation of efferent ductules
- some nephrons of regressing mesonephros become assoc with rete testis
Where do accessory glands form?
- seminal vesicles (vas deferens)
- prostate and bulbo-urethral (urethra)
3 components of external genitalia
- genital tubercle
- genital folds
- genital swellings
Congenital adrenal hyperplasia
- 21-hydroxylase deficiency (mediates prod of cortisol from chol by adrenal glands)
Formation of truncoconal septum
- ridges form on sides of conus cordis and truncus arteriosus
- form aorticopulmonary septum
- spirals
- valves form
Aortic arches
1 - maxillary artery and part of external carotid
2- stapedial
3- common carotid
4- R = part of R subclavian
L = part of aortic arch
6- proximal = pulm arteries
distal = ductus arteriosusDiaphragm development
- from septum transversum, oesophageal mesentery, pleuroperitoneal folds and secondary ingrowth from body wall
Developmental stages of the respiratory system
- embryonic
- pseudo glandular
- canalicular
- terminal sac (saccular and alveolar stages)
