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
2nd arch
Bone :-
Stapes
Styloid
Stlohyoid
Smaller horn of hyoid
Superior part of hyoid
Nerve - 7th
Artery - stapedial artery
Muscles
- Posterior belly of digastric
- muscle of face
- stylohyoid
- stapedius
3rd Arch
Bone
- interior surface of hyoid
- greater horn of hyoid
Nerve - glosopharyngeal nerve
Artery - common carotid, ECA, ICA
Muscle
Stylopharyngeus
4th arch
Bone - cartilage of larynx except epiglottis
Nerve - superior laryngeal nerve
Artery - Rt side = subclavian and left side = arch of aorta
Muscle
Muscle of pharynx except stylopharyngeus
Muscle of palate except tensor palatini
Cricothyroid
palatoglossus
ALL TONGUE MUSCLE FORMS FROM OCCIPITAL SOMITES EXCEPT PALATOGLOSSUS
6th arch
Cartilage of larynx except epiglottis
Nerve - recurrent laryngeal nerve
Artery - proximal by pulmonary artery, distally by ductus arteriosus
Muscle - muscle of larynx except cricothyroid
1) Trecher Collin syndrome
2) Pierre robin syndrome
1) 1st arch derivatives failure to differentiate
- c/f - facial asymmetry
- cloboma of lower eyelid
- external ear abnormalities
2) hypoplastic mandible
- glossoptosis which hamper palates fusion and give rise to cleft palate.
1) Structure from cleft
2) structure from pouch
2) pouch
A) 1st - middle ear, eustachian tube
B) 2nd - tonsillar fossa and tonsillar epithelium
C) 3rd - ventral = thymus, Dorsal = parathyroid 3 - Inferior parathyroid
D) 4th - ventral = ultimobrachial body - parafollicular cells ( C- cells of thyroid). Dorsal = parathyroid 4 - superior parathyroid
PARAFOLLICULAR CELLS - NCC> ULTIMOBRACHIAL BODY
CLINICAL
DIGEORGE SYNDROME
- 22q11 deletation
- 3rd pouch not differentiate
- no thymus and interior PT
- c/f recurrent infection and low calcium
1)
1st cleft - external auditory canal
Recent change - external auditory canal if invagination of 1st arch
2nd cleft - extend and joint with 6th forming cervical sinus
If it persist the swelling in ant. Of sternocleidomastoid - brachial cyst/sinus
Other cleft disappears.
Development of tongue
1) Epithelium
Anterior ⅔ - ectoderm
Posterior ⅓ - endoderm
2) muscle - from occipital myotome except palatoglossus
> On floor of 1st arch have two lingual and one tuberculum impar swelling - Anterior ⅔ of tongue
On floor on 2,3,4 arches there is hypobranchial swelling
- 3rd arch hypobranchial forms - Posterior ⅓ tongue
- 4th arch hypobranchial forms - Posterior most part of swelling
- 2nd arch hypobranchial forms - no contribution as 3rd attach with 1st
3) Nerve
Anterior ⅔ - general sensation - lingual (mandibular branch), taste - chorda tympani (7th)
Posterior ⅓ - both sensation - glossopharyngeal
Posterior most part - both sensation by vagus nerve (by superior laryngeal nerve)
ARCH POSTREMATIC. PRETREMATIC
1ST. mandibular. Chorda tympani from 7th of 2nd
arch
2nd Facial. Premitive nerve of other arch disappears.
1)Development of pitutary
2) development of thyroid gland
A) Stomodaeum (surface ectoderm) —⟩ rathke’s pouch —⟩ adenohypophysis —⟩ pars Anterior (distalis), pars intermedia, pars tuberalis
B) from diancephalon - neuroectodermal —⟩ infandibulum —⟩ pars nervosa
2) endodermal
Diverticulum derived from opposite to tuberculum impar —⟩ foramen caecum
Diverticulum descent and form thyroglossal duct —⟩ passes ant to hyoid bone —⟩ devide into two and form thyroid gland.
Development of face
1) Derived from
2) Lesions
3) Development of palate
4) lesions
1)
- frontonasal process - foramen and bridge of nose
- medial nasal process (Posterior) - philtrum, primitive palate
- lateral nasal process - ala of nose
- maxillary process - upper lips and cheek
- mandibular process - lower lips and chin
2) midline cleft upper lips - non fusion of MNP
- hare lip/ cleft upper lips - non fusion of maxillary with MNP
- oblique facial cleft - non fusion of maxillary with LNP
- cleft lower lips - non fusion of mandibular
3) MNP fuse and form inter maxillary segment which has 3 part
> Labial - philtrum
> Upper jaw - medial part of maxilla and 2 incisors
> Palatal - primary palate
> Maxillary process —⟩ 2 palatine process —⟩ 2° palate
4) partial cleft - non fusion of 2nd palate
Unilateral complete - one side 1st and 2nd
Bilateral complete - both side 1st and 2nd, Y shape.
