Embryology Flashcards
Primodial germ cell
Puripotent cell from epiblast at 2nd week –> yolksac endermal wall 4th week –> gonads 5th week
Craniopharaneal taratoma, sacrococcygeal teratoma
1) totipotent
2) puripotent
3) multipotent
4) oligopotent
5) umipotent
1) entire embryo and extra embryo - 8 cell stage
2) all germ layer
3) more the one category - hematopoietic germ cell
4) one category - vascular cell
5) one type - liver cell
Spermatogenesis
Capacitation
Puberty - spermatogonia (1) –> (mitotic) primary spermatocyte (16)(meiosis 1) (2n)–> secondary spermatocyte(n) –> (mieosis 2) spermatid (64-512) –> sperm/ spermatozoa
Independent assortment of maternal and paternal chromosome take place in first miosis division. (Primary to secondary)
Spermatogenesis - spermiogenesis
Spermiogenesis
- Nucleus - head of sperm
- Golgi apparatus - acrosomal cap
Mitochondria - spiral sheath around the middle piece
- centrosome - proximal centriole : sperical in neck. Distal : distal end of middle piece
- cytoplasm - shed as residual bodies of reguard
- cell membrane - covering.
Spermatogenesis - 74>64>60
Capacitation - 7 hrs in female genital track
Oogenesis
Mitochondrial genetic disorders
PGC turns into oogonium by 3rd month(mitosis) -> primary oocyte 5-7 month, arrest in deplotene phase(miosis 1 2n) -> puberty -> secondary oocyte (meiosis 2) -> arrest in metaphase -> sperm -> ovum
Most fertile period 3days - 2days before and 1day after ovulation.
Mitochondrial genetic disorders are due to maternal mitochondrial origin.
Fertilization
Acrosomal reaction (Acrosin, acid phosphatase, hyaluronidase) -> cortical reaction -> zona reaction. (Ampulla)
Zygotes in 12-24 hrs of fertilization.
2 cell on day 2 of fertilization
8-16 cell - morula - 3rd day.
32 cell - advanced morula 4th day
Blastocyst 41/2 day after fertilization.
Zona shedding - 5th day (hatching)
Implantation on posterior wall on 6th -7th day start and finish at 10th- 11th day with 100-250 cells.
Sequence
Fertilization — cleavage — compaction — cavitation — hatching — implantation — differentiation — bilaminar disc formation.
Second week of development
1) Blastocyst
2) circulation
3) Inner cell division
4) EEM
5) Chorion
6) Villi
Blastocyst - 58 cell, 5 inner and 53 outer
Intra desidual sign - gestational sac sign - deep implantation of embryo.
Cytrotrophoblast and syncytiotrophoblast
Lacuna in cytrotrophoblast.
15th day>12th day ——⟩ uteroplacental circulation
On day 17> 22 - fetoplacental circulation.
Blastocyst -> columnar cell -> epiblast on dorsal end -> amniotic cavity.
Blastocyst -> cuboidal cell -> hypoblast on ventral end -> form exocoelom membrane/ heuser’s membrane (flattened cell from hypoblast) -> enclosed primary yolk sac.
Double bleb sign - amniotic cavity + yolk sac cavity.
Extra embryonic mesoderm - from yolk sac > epiblast / hypoblast.
– Seperate outer and inner cell mass
– small cavitation forms following structure
1) connecting stalk - umbilical cord. Form wharton’s jelly.
2) splanchnopleuric layer(Visceral) - surrounding 2° yolk sac.
3) somatopleuric layer(parietal) - remaining EEM. Surrounding amniotic cavity. And other part.
Chorion - somatic EEM + cytrotrophoblast + syncytiotrophoblast
1° villi - cytrotrophoblast
2° villi - cytrotrophoblast + EEM
3° villi - cytrotrophoblast + EEM + blood capillary
Gastrulation
1) procodal plate
2) primitive streak
3) Germ layer
4) Notocord
5) Mesoderm
6) smooth muscle
-a)over dorsal aorta
B) pharyngeal arch arteries
C) iris
D) sweet and mammary gland
1) head end - from columnar hypoblast, form buccopharyngeal membrane, rupture at 4th week.
2) tail end - proliferation of epiblast, indicates beginning of gastrulation. At beginning of 3rd week (14-15 th day)
3) 1st - endoderm from epiblast
2nd - interembryonic mesoderm from primitive streak
3rd ectoderm - remaining epiblast
Note : ALL GERM LAYER EPIBLAST > YOLK SAC
OCCUR CRANIOCAUDAL
4) from mesoderm, stimulate neural tube formation
Primitive knot —⟩ primitive pit(blastopore) —⟩ notocordal process —⟩ notocordal canal —⟩ notocordal plate —⟩ definitive Notocord.
Structure - nucleus pulposus > apical ligament of dens
Persist - CHONDROMA - PHYSALIFEROUS CELLS
5)
Paraxial mesoderm - somites
Intermediate mesoderm - urogenital system
Lateral - divided into two part by cavity
- cavity = pericardium, pleural, peritoneal
- splanchnopleuric (Visceral) - near intermediate, heart tubes, smooth muscle, splanchnopleuric layer of body cavity.
- somatic (parietal) - appendicular skeleton upper limb and lower limb bone, somatic layer of body cavity.
6)
A) splanchnopleuric of lateral mesoderm > paraxial mesoderm
B) neutral crest cells
C) neuro ectoderm
D) surface ectoderm
Somites
Three part -
Scleroderma
Dermamytome - two divisions myotome and dermatome
1st pair - 20 th day
Add 3 each day
At end of 35th day(5th week) 42-44
After 5th week - some occipital and coccygeal disappearing – remain 37
Order of appearance - occipital –⟩ cervical - thoracic - lumbar - sacral - coccygeal
1) scleroderma - axial skeleton
- ventral = body of vertebrae
- Dorsal = spine of vertebrae
- lateral = vertebral arch
Failure to fuse - meningoce, myelocele (meningis + spinal cord), Spina bifida occult ( truft of hair on defect)
2) myotome - skeleton muscle
- occipital = tongue muscle
- pre occipital = extral occular
- cervical = diaphragm
3) dermatome - skin
-
Folding of embryo and formation of gut
1) septum transversum
2) membrane
3) Allantoin
4) Gut
Embryo fold - cranial, caudal and lateral.
1) contribute in diaphragm , liver, fibrous pericardium.
2) buccopharyngeal membrane - 4th week
cloacal membrane (both doesn’t contain mesoderm) - 7- 9 th wk and connect chloaca and anal pit (proctedum)
3) protrusion of yolk sac. Remaining yolk sac - veteline duct and umbilical vesicle
Gut derived from ectoderm of yolk sac.
A)Fore gut - upto major deodenum papilla ( 2nd part) - celiac trunk, sympathetic = greater splanchnic nerve (T5 - T9), parasympathetic - vagal
B) mid gut - upto right ⅔ transverse colon - superior mesenteric artery, sympathetic - Lesser splanchnic nerve ( T10 - T11), parasympathetic - vagus
C) hind gut - distal to allantoin is known as cloaca, inferior mesenteric artery, sympathetic - least splanchnic nerve T12 and lumbar splanchnic L1-2, parasympathetic - nervi erigentes ( S2 S3 S4)
Neurulation
1) neural crest cell
2) neural tube
3) cranial part
3rd week.
Notocord signal –⟩ ectoderm thickening –⟩ neuro ectoderm, surface ectoderm, neural crest cells —⟩ neural fold —⟩ neural groove —⟩ neural tube.
1) 4th germ layer, mesenchyme/ migratory cells.
In trunk region
- melanocytes
-Sensory ganglia
- sympathetic and enteric neurons
- Schwann cells
- adrenal medulla cells
In cranial region
- craniofacial skeleton
- neurons from cranial ganglion
- satellite glial cells
- C cell of thyroid gland
- conotruncal septum in heart
- odontoblasts
- smooth muscle cells to blood vessels to face and forebrain.
2) connected to amniotic cavity.
Three part -
A) Cranial neuropore - close at 25th day. Remnant - lamina terminalis. Anencephaly.
B) Caudal neuropore - close at 28 th day. Remnant - terminal ventricle. Spina bifida.
Neural tube.
Two divisions : Cranial - brain, caudal - spinal cord.
Neural Tube defect - Spina bifida, anencephaly, cranio rachisehisis - intire neural tube is open.
3)
A) prosencephalon
- Telencephalon - cerebrum, corpus striatum
- diancephalon - Every type of thalamus,pars nervosa, retina, optic nerve
B) mesencephalon - mid brain
C) rhombencephalon
- metencephalon - pons and cerebellum
- myelencephalon - medulla
- pineal gland - part of epithalamus - diancephalon
- medial and lateral geniculate body - part of metathalamus - diancephalon
- substatia nigra - mesencephalon.
Organizer
Any part of embryo that exert morphogenetic stimulus on adjacent tissue.
Primary - blasto pore induces differentiation of Notocord.
Secondary - Notocord induce development of neural tube
Tertiary - neural tube induce somites formation.
Cell division
Mitosis - 2n ——⟩ 2n
Meiosis 2n ——⟩ n
Mieosis in two phase
- prophase 1 - leptotene, zygotene, pachytene, diploten, diakinesis.
- metaphase 1
- anaphase 1
- telophase 1
Second stage
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
Stages of development
—⟩ pre - embryonic period (upto 2 weeks)
Fertilization till two layered germ disc.
—⟩ embryonic period (3-8 weeks)
Trilaminar germ layer to early organogenesis
—⟩ fetal period (9 weeks till birth)
Growth and specialization of body structure.
Development of pharyngeal arch
4th week NCC migration to future neck with mesenchymal condensation
NCC > mesoderm
Arise 6 arch —> 5th disappearing —≥ 5 left
Endoderm - pouch
Ectoderm - cleft
Pharyngeal membrane
- ectoderm meet endoderm with in between mesoderm
5 in number
1st - tympanic membrane
Other disappears.
1st pharyngeal arch
> cartilage
- malleus and incus
- ant. Lig of malleus
- sphenomedibular ligament
- maxilla, zygomatic, cover, palatine, sphenoid
- majority of skull bone.
Nerve - mandibular
Artery - maxillary
Muscle :-
Tensor tympani
Tensor palatini
Ant. Belly of digastric
Mylohyoid
Pterygoid
Muscle of mastication
