Embryology Flashcards
Stem cells.
Describe cleavage.
-within uterine tube
-unicellular zygote divides by mitosis or cleavage to become multicellular embryo
-each daughter cell = blastomere
-no increase in size due to zona pellucida
Describe morula.
-in uterine tube
-blastomeres divide into ball of 16-32 cells in zona pellucida
Describe a blastocyst.
-enters the uterus & hatches from zona pellucida = develops a cavity = ‘blastocoele’ = yolk sac
-differentiation of inner cell mass = embryo blast surrounded by outer cells = trophoblast
Describe the blastocyst hatching.
-from zona pellucida
-accommodate implantation
-hatching due to pressure of expanding blastocyst & enzymatic dissolution of zona pellucida
Describe the inner & outer cells of the blastocyst.
- Inner - embryoblast (forms entire embryo)
- Outer - trophoblast
>expand to form extra embryonic membrane (amnion, yolk sac, allantois, chorion) related to placenta
Describe the epiblast & hypoblast.
-embryoblast differentiates to form bilaminar disc of epiblast (dorsal) & hypoblast (ventral)
Describe gastrulation.
3 germ layers
Gastrulation summary.
Describe the germ layer derivatives.
-inner -> embryoblast -> epiblast
-primary germ layers: ectoderm, mesoderm, endoderm
>ectoderm: epidermal, lining of oral, nasal cavity & anus, corneal epithelium, NS
>mesoderm: CT, muscle tissue, mesothelium, CVS, urogenital tract
>endoderm: epithelial lining & glands of digestive & respiratory system
Describe the formation of notochord.
-derived from mesoderm
-transient structure
-provides direction
-basis for vertebral column
-provides direction & contributes to vertebra & intervertebral discs
-induces ectoderm to differentiate into neuroectoderm
What are the functions of the notochord?
- Primitive axis of embryo = rigidity
- Basis for development of axial skeleton
- Future site of vertebral bodies
- Development of CNS
Describe the formation of neural tube.
-derived from ectoderm
-basis for CNS
-cranial = brain
-caudal = spinal cord
-notochord = direction & contributes to formation of vertebral column
Describe the mesoderm: intra-embryonic.
Describe the mesoderm: paraxial
-somitogenesis
-differentiates into somitomeres on each side of neural tube
-differentiates further into somites
What are the major somites?
-sclerotome: vertebrae, portions of skull, axial skeleton
-myotome: striated muscles of head, trunk, limbs
-dermotome: dermis of dorsal/back regions
Segmented somites (picture).
Describe mesoderm: intermediate.
-differentiate into urogenital system
>paired kidneys
>paired adrenal gland cortex
>paired gonads
>female & male reproductive ducts
Describe mesoderm: lateral plate
-somatic (parietal) = dorsal & associates w ectoderm
>contributes to serous membranes lining the peritoneal, pleural, & pericardial cavities
-splanchnic (visceral) = ventral & associates with endoderm
>contributes to CVS, blood, kidneys, smooth muscles
Describe mesoderm: extra-embryonic.
-derived from epiblast (originally from inner cell mass or embryoblast)
-contributes to formation of yolk sac, amnion, allantois & chorion
-vital functions in maternal-fetal protection, nutrient & waste exchange
Placenta types. (Picture)
Describe teratogens.
-any factor that causes congenital defects during fetal growth & development
>genetics
>radiation
>chemical agents (ex. Nicotine, drugs, alcohol
>infectious agents (ex. Aka bane virus, bovine viral diarrhea virus)
>hormones (ex. Anti-paramesoephric duct hormone in freemartins)
Describe congenital defects of teratogens.
- Reproductive
-free Martin
-cryptorchidism - Alimentary
-cleft palate
-atresia ani - Urinary
-persistent urachus - Neuro
-hydrocephalus
-cerebellar hypoplasia
-spina bifida - CVS
-patent ductus arteriosus
-ventricular septal defect
-persistent R aortic arch
-portocaval shunt - Respiratory
-brachycephalic airway syndrome - Body wall
-umbilical hernia
Describe undifferentiated gonads.
- Genital ridge: medial part of mesonephros (early kidney) & differentiate into capsule, stroma & CT of gonad
- Coelomic epithelium: covers gentian ridge & differentiate into sex cords (sertoli or granulosa cells) of gonad
- Primordial germ cells (PGC): unipotent cells that migrate from wall of yolk sac & differentiate into spermatogonia or oogonia between sex cords or sertoli or granulosa cells in testes or ovaries
Describe differentiated gonads.
- Paired testes: presence of Y chromosome (XY) = SRY gene that encodes for a testis determining factor & Sertoli cells produce AMH - Müllerian ducts degenerate & testes & wolffian ducts (Epididymus, vas deferens, ejaculatory duct, seminal vesicles) develop
- Paired ovaries: absence of Y chromosome (XX), wolffian ducts degenerate & ovaries & Müllerian ducts (oviducts, uterus, cervix, cranial vag) develop
Gonadal differentiation.
Gametogenesis.
