Early Development Flashcards
Where do primordial cells live ?
Yolk sac
What week do primordial cells emerge?
4th week
What week do primordial cells migrate ?
6th week
Where do primordial cells undergo meiosis?
Gonads
What is the importance of meiosis one ?
replication of DNA with crossover
without splitting of centromere
What is the importance of meiosis two ?
centromere splitting
When do the male primordial cells go dormant ?
@ 6th week
How long are the male primordial cells dormant for ?
6th week till puberty
When does meiosis start for males ?
@ puberty
What are the male cells that arise from primordial cells ?
Type A spermatogonia undergo mitoiss = stem ells
Type B spermatogonia undergo meiosis
What type of cell is approaching meiosis one ?
”- gonia” cells
When does female oogonia replicate?
6th week to 4th month
When is there a maximum number of oocytes in a females ?
5th month
When do oogonia enter meiosis one ?
5th month
What are the arrested times of oocytes in the females ?
1st- prophase of meiosis 1 :5 mth
2nd- metaphase of meiosis II : hrs before ovulation
When does meiosis I go to completion ?
during time of menses to form secondary oocyte
How does secondary oocyte go to completion?
With fertilization from sperm
Where do the reproductive organs arise from ?
intermediate mesoderm
What is emerges from the intermediate mesoderm
Urogenital ridge
What does the primary sex cords give rise to?
Males–> seminiferous tubules
Females–> primordial follicles
What is the name of the male genital tract ?
Mesonephric duct ( wollfian)
What influences the male genital tract ?
Testosterone
What is the name of the female genital tract?
paramesonephric ducts ( mullerian)
What influences the female genital tract ?
estrogen
What differentiates the indifferent gonads ?
Y chromosome with the SRY gene & TDF
When do males produce testosterone?
by the 8th week by Leydig cells
what triggers the sec cords in a males?
testosterone from the leydig cells
What gives rise to male external genitalia in a male?
Dihydrotestosterone by 5 alpha reductase
How does the ovary form?
absence of Y chromosome
What is a Gartner duct ?
Remnants of mesonephric duct
Describe how a bicornuate uterus is formed?
improper fusion of the paramesonephric duct
When are the external genital distinguishable ?
12 week
What does the tubercle, folds, and swellings form in the females?
tubercle- clitoris
folds- labia minora
swellings - labia majora
What does the tubercle, folds, and swellings form in the male?
tubercle- glands penis
folds- ventral side of penis
swellings- scrotum
Hypospadias
Ventral opening
defect in folds
Epispadias
Dorsal opening
body wall defect
What needs to be removed for proper implantation?
Zona pellucida
What is the first form of blood supply for the fetus ?
yolk sac until 6th week
Where does the blood supply come from after the 6th week?
liver, spleen , thymus
Where does blood supply arise in the last trimester of the fetus s?
bone marrow
What sustains life for the first trimester?
Corpus lutem
What is the hormone produced that sustains the first trimester?
Progesterone
What forms the 3 germ layers and the notochord ?
migration of epiblast
What are the three sections of mesoderm ?
paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm
What does the paraxial mesoderm give rise to?
sclerotome: axial skeleton
myotome : muscles of the body & limbs
dermatome: dermis of the back
What does the lateral mesoderm give rise to ?
somatic : lateral fold
splanchnic: heart
What does endoderm give rise to?
epithelial lining : GI tract, Lower respiratory system, genitourinary system, pharyngeal pouches
parenchyma of: Liver, pancreas, submandibular, sublingual glands
Endocrine: parathyroid glands, follicles of thyroid
What does mesoderm give rise to?
Musculoskeletal, cardiovascular, genitourinary
Spleen
What are the layers of that the adrenal is derived from?
Cortex- mesoderm
medulla - neural crest
What does neural crest cells give rise to ?
Peripheral nervous system, head ( pharyngeal arch), heart (cushion, aorticopulmonary septum )
Parafollicular cells (C cells)
What does neuroectoderm give rise to?
Neural tube - CNS ( barin , spinal cord)
posterior pituitary
What does surface ectoderm give rise to ?
Skin, hair, nails
anterior pituitary
anal canal
parotid gland
What is a sacrococcxygeal teratoma ?
failure of primitive streak to regress
What is a chordoma?
remnant of the notochord
What does the dorsal ramus affect?
Sensory and motor of the back
What does the ventral ramus affect?
Sensory and motor of the anterior & limbs
What is the components of the spinal nerve ?
Ventral and Dorsal
Where are somatic sensory unipolar neurons found?
PNS
Where are somatic motor multipolar neurons found ?
CNS
Pia mater
attached to the cord
ends at L2
forms denticulate ligament & filum terminale
Dura mater
ends at S2
dense outermost layer
Arachnoid mater
ends at S2
between dura and pia
What are the meningeal spaces ?
subarachnoid space : CSF filled
epidural space: outside the dura, contains fat and venous plexus
What does the autonomic system control ?
smooth muscle
cardiac muscle
glands
What is the sympathetic cord segments for body wall and limbs?
T1- L2 lateral horn
What are the segments of sympathetic COLLATERAL ?
Lumber splanchnic L1-L2
Thoracic splanchnic T5-T12 ( FG:T5-9, MG:T10-11, kidney gonadsT12)
What are the 3 sympathetic chain segments?
Thoracic viscera T1-T5
Head T1-T2
Body wall and limbs T1-L2
Where does parasympathetic innervate ?
visceral organs of head and body cavities
limited vascular
What are the parasympathetic innervations ?
Craniosacral
CN III, VII, IX, X
S2, S3, S4
Where do parasympathetic neurons terminated ?
on the visceral organ
What does pelvic splanchnic innervate ?
rectum
bladder
erectile tissue
What does Vagus nerve innervate
Thoracic and abdominal viscera
What does parasympathetic CN III innervate?
Ciliari ganglion (sphincter pupillae, ciliary muscle)
What does parasympathetic of CN VII innervate ?
pterygopalatine ganglion (lacrimal, nasal, sublingual) submandibular ganglion (submandibular, sublingual)
What does parasympathetic of CN IX innervate?
Otic ganglion ( parotid gland)
