development mini1b

• 1. spermatogonial- spermatogonia differentiate into primary spermatocytes (2n)
• 2. spermatocyte- meiosis 1 and 2 (4n then 2n)
• 3. spermiogenesis- spermatids differentiate into spermatozoa (1n)

before birth primary oocytes enter 1st stage of meiosis and are arrested in DIPLOTENE stage by OMM released by follicular cells

• 5 mts- 7 million oogonia
• birth- 600,000 to 2 million
• buperty- 400,000

ampullary region of fallopian tube

• primary- 4n
• secondary- 2n + 1 polar body
• mature- 1n + 3 polar bodies

• releases egg to infundibulum, then if egg is fertilized, will turn into the CORPUS LUTEUM which maintains hormone release
• -if no fertilization with shrivel into CORPUS ALBICANS.

• *sperm passes thru corona radiata*
• removal of glycoprotein and cholesterol coat of sperm (prevents zona pellucida binding) by the uterus and fallopian tube so they can penetrate the corona radiata

• *sperm penetrate the zona pellucida*
• -hyalauronidase, acrosin are main enzymes

• 1-capacitation(corona radiata penetration)
• 2-acrosomal reaction(zona pellucida penetration)
• 3- spermatazoa fuses with the 2 oocyte PM
• 4-fastblock- depol of PM to prevent other sperm bind
• 5-slowblock(cortical rxn)- causes high Ca stores to cause release of cortical granules
• 6-zonal rxn- ez from granules alter PMr and zona pellucida
• 7- polyspermia prevented and 2 oocyte completes meiosis 2 to yield ovum and 2nd polar body
• 8- formation of female PRONUCLEUS
• 9-male PRONUCLEUS formation
• 10-pronuclei fusion, fertilization complete, ZYGOTE produced

rapid mitotic divisions in which the cells DO NOT grow in size. first occurs 30 hours after the beginning of fertilization

weeks 3-8

• -about 12-16 cell ball
• -forms at about 3 days
• - as cleavage continues morula passes down FT towards the uterus

• day 4-embryo enters uterine cavity
• - inner cells (embryoblast) become the embryo proper
• -outer cells (trophoblast) form part of the placenta
• embryoblast+ trophoblast= blastocyst
• -blastocyst in uterine for 2 days as zona pellucia disapears

begin penetration of trophoblast thru uterine epithelium toward uterine stroma

• 1- ovulation
• 2- fertilization
• 3- cleavage, morula, blastocyst
• 4- zona pellucida disappearance
• 5- trophobladst invades superficial epithelia

-epiblast formation (columnar) + hypoblast formation (cuboidal)= BILAMINAR GERM DISC

trophpblast divison = syncitiotrophoblast and cytotrophoblast

• day 8
• small cavity appears within the epiblast becoming amniotic cavity, cells lining the cavity are amnioblasts, which form the amnion

• embyro completely embedded in uterine endometrium and fibrin plug closes gap
• *embryo seperated from cytotrophoblast above by amnotic cavity and below by th primitive yolk sac

line primitive yolk sac

• -uterine epithelium is relining where penetrated
• -maternal sinusoids fuse with syncitiotrophoblastic lacuna, establishing uteroplacental circulation
• -mesenchyme formation
• -chorionic cavity formation from extraembryonic mesoderm

secondary yolk sac formtion

-primary stem villi formation by cytotrophoblast cells

• forms around day 13 and will form part of the umbilical cord
• -only place where extraembryonic mesoderm traverses the chorionic cavity (an expansion of the extraembryonic coelom)

oropharygeal plate and oropharyngeal membrane formation

• 1-trophoblast differentiation
• 2-lacunar network formation=> uteroplacental circ formation
• 3-primary chorionic villi
• 4-implantation completion
• 5-amnion and 2 yolk sac formation
• 6-bilamina germ disc formation
• 7-oropharyngeal plae development

implantation of blastocyst into the internal os, leads to severe bleeding during birth

• 1- cytokines like IL-2
• 2- MHC-1B (HLA-G)

• -happens 3rd week
• 1- primitive streak formation
• 2- triaminar formation
• 3-notocord formation

• epiblast cells migrate to primitive streak and slip under (with direction of FGF) and will form endoderm, mesoderm and ectoderm
• -axis also developes

• epiblast cells migrate thru primitive pit toward oropharyngeal plate and form notocord(mesodermal cells)
• **essential for neural tube deelopment**

essential for forbrain development

where cloacal and orophayngeal membranes form

in front of prechordal plate where mesodermal cells will give rise to the heart

• day 16
• -early blood formation and urinary bladder
• -vessels become the umbilical a. and v.
• -will become the median umbilical ligament in adults

end of 4th week

muscles

urgenital system

muscles and divides body cavities

heart, lungs, stomach, gut and spleen

inversion of all internal organs to opposite side

• sonic hedgehog
• produced by primitive node and is invilved in midline formation

tumor that arises from primitive streak that does not degenerate when it should (end of the 4th week)

• associated with maternal diabetes
• -not enough mesodem migrates to lateral plate mesoderm and causes fusion of limb buds and other defects

• week 3
• -mesodermal origin
• -induces ectoderm to thicken and form neural plate

occurs at the 5th somite and result in formation of neural tube

crest of the wave of neural tube formation and will detach when neural tube closes and become the spinal ganglion

epidermis

• - causes ectoderm--> epidermis
• - mesoderm--> lateral plate and intermed. mesoderm
• -**inactivation causes neural plate induction**

cranial at day 25-26

• caudal at 27-28
• **signal completion of neuralation, and ventricule and spinal cord formation begins**

• 5th week
• forms the lens of the eye

gives rise to 2 cerebral hemispheres

• CNS, PNS, sensory epithelim, epidermis, anterior pituitary, enamal, derivatives of neural crest cells
• (contact with the external world)

• form from paraxial mesoderm
• 42-44 pairs by the 35th day
• -differentiation occurs by start of the 4th week

somite cells that differentiate into vertabra and ribs

retain innervation from segment of origin regardless of migration

by 8th week intraembryonic cavity gives rise to peritoneal, plearal and pericardial cavities

• starts in yolk sac and allantois, then liver, then bone marrow
• -vasculogenesis- vessels arise from blood islands
• -angiogenesis- vessels arise from existing vessels

• day 21
• heart tubes fuse into single tube that starts to beat

adrenal cortex, spleen, CT, cartilage, bone, blood, urogenital, serous membranes lining body cavities

forms part of diaphragm

anterior abdominal wall defect(lateral folding failure) that results in visceral organs outside of the body

neural cells undergo this process after neural tube formation, then migrate to the underlying mesoderm

• first- can be several different types
• later- only dorsal derivitives
• last- pigment cells

bones of face and skull, adrenal medulla,glial cells, odontoblasts, septum of heart, thyroid c cells (calcitonin)

form from NC cells in the trunk region

form from NC cells in the cranial region

• 1-ventrolaterally- DRG
• 2-ventrally- adrenal medulla and SNS
• 3- dorsolaterally-melanocytes

• 1-enteric crest-PSN of gut
• 2-cardiac crest cells- large ateries and aorticopulmonary septum
• 3- pharyngeal arches

• 1-cardiac septum defects
• 2-DiGeorge syndrome- reduced function of thymus, thyroid and parathyroids

• *starts before closure of neural folds*
• -midbrain-r2= paryngeal arch->jawbone, facial bones, incus and maleus
• -r4-phar. arch 2=hyoid carltilage and stapes
• -r6-r7= 3rd PA to form lower hyoid bone

aganglionic megacolon

• secreted by sycitiatrophoblast to tell ovary to retain the corpus luteum which will continue to secrete progesterone and keep endometrial functional layer of uterus
• *hormone for prego testing*