Download Body cavities

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Development of the nervous system wikipedia, lookup

Transcript
Body cavities
Formation of body cavities
• At ^ end of ^ 3rd week: ^ lateral plate mesoderm which is
involved in ^ formation of body cavity, it will differentiate into
2 layers ( a) ^ parietal (somatic) layer adjacent to ^ surface
ectoderm & continuous with extra-embryonic parietal
mesoderm layer covering ^ amnion. (b) ^ visceral
(splanchnic) layer adjacent to ^ endoderm & continuous
with^ visceral layer of extra-embryonic mesoderm covering ^
yolk sac.
• During ^ 4th week, ^ sides of ^ embryo begin to grow ventrally
forming 2 lateral body wall folds. These folds consist of ^
parietal layer of lateral plate mesoderm. ^ endoderm also
folds ventrally & closes to form ^ gut tube.
• By ^ end of 4th week, ^ lateral body wall folds meet in ^
midline & fuse to close ^ ventral body wall. This closure is
aided by head & tail folds that cause ^ embryo to curve into ^
fetal position.
• Closure of ^ ventral body wall is completed except in ^
connecting stalk, similarly closure of ^ gut tube is completed
except for vitelline duct.
Serous membranes
• Cells of ^ parietal layer of lateral plate mesoderm lining ^
intra-embryonic cavity become mesothelial & form the
parietal layer of ^ serous membranes lining ^ outside of ^
peritoneal, pleural, & pericardial cavities.
• Similarly, cells of ^ visceral layer of lateral plate mesoderm
form the visceral layer of ^ serous membranes covering ^
abdominal organs, lungs, & heart.
• Visceral & parietal layers are continuous with each other at
the dorsal mesentery . Which suspends ^ gut tube rom ^
posterior body wall into ^ peritoneal cavity.
• Dorsal mesentery extends from ^ caudal limit of ^ foregut to ^
end of hindgut.
• Ventral mesentery exists only from ^ caudal foregut to ^
upper portion of ^ duodenum & results from thinning of
mesoderm of septum transversum.
• These mesenteries are double layers of peritoneum that
provide a pathway for blood vessels, nerves,& lymphatics to ^
organs.
• ^ septum transversum is a thick plate of mesoderm occupying
^ space between ^ thoracic cavity & ^ stalk of yolk sac.
Diaphragm & thoracic cavity
• Diaphragm divides ^ body cavity into ^ thoracic & peritoneal
cavities.
• It develops from 4 components:(a) septum transversum
(central tendon) (b) pleuroperitoneal membranes. (c) dorsal
mesentery of ^ esophagus, & (d) muscular components from
somites at cervical level s three to five (C3-5) of ^ body wall.
• Since ^ septum transversum is located initially opposite
cervical segments three-five & since muscle cells for ^
diaphragm originate from somites at these segments, ^
phrenic nerve also arises from these segments of ^ ^ spinal
cord (C3,4,&5) keep ^ diaphragm alive.
• Congenital diaphragmatic hernias involving a defect of ^
pleuroperitoneal membrane on ^ left side occur frequently.
• ^ thoracic cavity is divided into ^ pericardial cavity & two
pleural cavities for ^ lungs by ^ pleural cavities for ^ lungs by
^ pleuropericardial membranes.
• Initially, ^ gut tube from ^ caudal end of ^ foregut to ^ end of
^ hindgut is suspended from ^ dorsal body wall by dorsal
mesentery.