CRANIATE EMBRYOGENESIS

7/28/2019 CRANIATE EMBRYOGENESIS

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Mrs. Ofelia Solano SaludarDepartment of Natural Sciences

University of St. La Salle


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YOUTH IS ABLUNDER,

MANHOOD ASTRUGGLE,

OLD AGE A REGRET.

Benjamin Disraeli on life history:


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OVIPARITY- egg-laying; contains yolk and

albumen to support development

VIVIPARITY- offspring is born alive

EUVIVIPARITY- maternal tissues provide

nutrition, e.g. histotrophic (embryotrophic)

nutrition derived from glandular secretions,

e.g. placenta

OVOVIVIPARITY- egg providesnourishment throughout

pregnancy, mother provides

protection and oxygen; e.g. shark
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1. EXTERNAL- oviparous forms

2. INTERNAL- viviparous forms

Spermatophore- gelatinous packet of sperm is

placed in the cloaca of female by the male, or

picked up by lips of females cloaca, e.g.

urodeles Spermathecae- crypts in the female tract

containing stored sperm which may fertilize

eggs when conditions become suitable

censored


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MICROLECITHAL, OLIGOLECITHAL orISOLECITHAL- little amount of yolk; yolk evenly

distributed: echinoderms, Amphioxus, mammals

MESOLECITHAL- moderate amount of yolk found invegetal pole: many fishes, lampreys, amphibians

MACROLECITHAL- large amounts of yolk found:

shark, monotremesTELOLECITHAL- yolk concentrated on one pole;

birds, reptiles, most nontherian craniates


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AMPHIOXUS

AMPHIBIAN


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BIRD

EMBRYOGENESIS


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YOLK SAC-surrounds the yolk; Meckels diverticulum is

vestigial yolk sac of man

CHORION- lines eggshell

or mothers uterus

AMNION- preventsdessication of embryo

and buffers fetus against

mechanical trauma

ALLANTOIS- respiratoryorgan, site of exchange

of nutrients and metabolic

wastes between mother

and embryo; proximal part becomes urinary bladder


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SIMPLE YOLK SAC-serves as a membrane for absorbing oxygen

and nourishment from maternal tissues; e.g. viviparous anamniotesCHORIOVITELLINE- yolk sac lies against the chorion; e.g.

marsupials

CHORIOALLANTOIC- chorioallantoic membrane is in direct contact

with maternal uterine lining; reptiles, monotremes, eutherians

NONDECIDUOUS vs. DECIDUOUS-fetal membranes peel away

without shedding of uterine lining (ungulates), or disengage with

bleeding from the invaded tissues of uterine lining (man)

CHORIONIC VILLImaybe arranged in cotyledonary (patches), zonary

(band), diffuse, or discoidal patterns

a device which allows an embryo to obtain food

from the mother. In return the embryo provides bodily waste and

eventually, birth pains, stretch marks & sleepless nights.


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Feeding the kids to be


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The mutual associations established among

cells and tissues determine the eventual

developmental outcome.

SCLERO

TOMES

CARTI

LAGES

VERTE

BRAE

SPI

NAL

CORD

NEU

RAL

TUBE

INDUCTION-stimulatory effect betweendeveloping parts of the embryo


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MORPHOGENS- inductor (signaling) proteins

expressed by specific homeotic genes that induce

organization of the germ layers and participate in the

differentiation of specialized tissues from embryonic

mesenchyme.

HOMEOTIC GENES- Hox gene clusters determine thefates of individual segments in Drosophila and craniates

Sonic Hedgehog- participate in differentiation of the

notochord, early neural tube, fins or limbs

Chordin- secreted by genes in the dorsal lip of the

blastopore; body axis-forming activity in early

gastrulation


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MORPHOGENS

MESENCHYMEdendritic, undifferentiated embryonic cells

BLASTEMAtotipotent mesenchymal aggregates


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EPIDERMIS NEURAL PLATE NEURAL CREST

Epidermis

Stomodeum-

mouth; Rathkes

pouch;

mammalian

enamel

Proctodeum-cloacal opening

Extraembryonic

membranes

Telencephalon- cerebral

hemispheres

Diencephalon- thalamus;

Mesencephalon-optic lobes

Metencephalon-

cerebellum

Myelencephalon- medulla

oblongata

Olfactory, otic, optic,

epibranchial placodes and

neuromasts

Neural tube- spinal cord

Ganglionic neural

crest

Neuroglia (Schwann

cells)

Ectomesenchyme-

melanocytes

Visceral skeleton

Adrenal medulla


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EPIMERE MESOMERE HYPOMERE

SOMITE

Dermatome-

dermis

Myotome-

body

musculature

Sclerotome-

vertebral

column

NEPHROTOME

Kidney and

urogenital

ducts:

pronephric

tubules and

duct,

mesonephric

tubules, renal

cortex

Somato

pleure

Splanchno

pleure

Limbs

Parietal

peritoneum

Genital ridge-gonads

CT of skeleton

and body wall

Blood vascular-

heart, vessels

Visceral

peritoneumMesenteries

Extraembryonic

membranes


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FOREGUT MIDGUT HINDGUT

Pharynx- oral and

nasal cavities andderivatives;

pharyngeal pouches

Posterior foregut-esophagus, lungs

buds (trachea)

Stomach

Liver

Pancreas

Small andlarge

intestines

Allantois-

urinarybladder

Urogenital

sinus- cloaca


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QUESTIONS?


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QUESTIONS?


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Quiz next meeting.

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CRANIATE EMBRYOGENESIS