Body Folding and Body Cavities

Question 1

Intraembryonic coelom

Answer 1

divides lateral mesoderm into :

Somatic layer of lateral mesoderm

Splanchnic layer of lateral mesoderm

Question 2

Somatic layer of lateral mesoderm

Answer 2

continuous w/ extraembryonic mesoderm covering amnion

Question 3

Splanchnic layer of lateral mesoderm

Answer 3

continuous w/extraembryonic mesoderm covering umbilical vesicle

Question 4

Somatopleure

Answer 4

somatic mesoderm and overlying embryonic ectoderm form body wall

Question 5

Splanchnopleure

Answer 5

splanchnic mesoderm and underlying embryonic ectoderm form embryonic gut

Question 6

embryonic planes

Answer 6

establishment of body form caused by folding of flat trilaminar embryonic disc into a cylindrical embryo

Rapid growth of embryo

Simultaneous at caudal, cranial and sides

Question 7

Embryo elongation cranially and caudally

Answer 7

cranial and caudal regions move ventrally at week 4

Question 8

neural folds during embryonic folding

Answer 8

project dorsally into amniotic cavity

grow cranially beyond oropharyngeal membrane and overhang primordial heart

Question 9

Septum transversum during embryonic folding

Answer 9

translocated to ventral surface

Question 10

Head Folding

Answer 10

septum transversum, primordial heart, pericardial coelom, oropharyngeal membrane now on ventral surface

Question 11

Arrangement of embryonic coelom

Answer 11

Affected during head fold

Question 12

After head folding

Answer 12

Pericardial cavity is ventral

pericardioperitoneal canals run dorsally on each
side of foregut

intraembryonic and extraembryonic coeloms in communication

Question 13

Folding of the caudal end of embryo

Answer 13

due to growth of distal neural tube

Question 14

Cloacal membrane

Answer 14

becomes anus in future

Question 15

Lateral Folds

Answer 15

Rapid growth of SC and somites produce R/L lateral folds

Extend ventrally toward midline
Creates a cylindrical embryo

Question 16

Gastroschisis

Answer 16

protrusion of viscera, site of abdominal defect is to the right of the umbilical cord

bowel uncovered and floating in amniotic fluid

Question 17

Congenital epigastric hernia

Answer 17

midline bulge of abdominal wall located between xiphoid process and umbilicus

bowel not exposed to amniotic fluid because it remains covered by skin and tissue

Question 18

Intraembryonic coelom

Answer 18

divided into pericardial cavity, pleural cavities and peritoneal cavity

Question 19

Body cavities lined with mesothelium

Answer 19

parietal wall: derived from somatic mesoderm

visceral wall: derived from splanchnic mesoderm

Question 20

heart and pericardial cavity are relocated ventrally, anterior to foregut

Answer 20

during formation to head fold

Question 21

Dividing the body cavity

Answer 21

partitions form in each pericardioperitoneal canal separating:

1. pericardial cavity from pleural cavities
2. pleural cavities from peritoneal cavity

Question 22

pleuropericardial folds enlarge and form:

Answer 22

pleuropericardial membranes: project into pericardioperitoneal canals

Question 23

bronchial buds:

Answer 23

grow into pericardioperitoneal canals, extend into body wall

Question 24

mesenchyme splits into:

Answer 24

outer layer: thoracic wall

Inner layer: fibrous pericardium

Question 25

pleuroperitoneal membranes

Answer 25

pleuroperitoneal folds enlarge and become membranous, forming these membranes Form as developing lungs & pleural cavities expand/invade the body wall Attached dorsolaterally to the abdominal wall

Question 26

septum transversum

Answer 26

expands and fuses with dorsal mesentery of esophagus and pleuroperitoneal membranes: central tendon of diaphragm

Question 27

pleuroperitoneal membranes

Answer 27

fuse with dorsal mesentery of the esophagus & septum transversum → primordial diaphragm

Question 28

Congenital diaphragmatic Hernia

Answer 28

Viscera bulge into pleural cavity lung maturation may be delayed: polyhydramnios may be present left side typically effected, but can be corrected at birth

Question 29

Three phases of human development:

Answer 29

1.growth:involves cell division and elaboration of cell products 2. morphogenesis: development of shape, size and other features of particular organ - controlled by expression of genes in orderly sequence 3.differentiation, cells are organized in a precise pattern of tissues & organs that are capable of performing specialized functions

Question 30

Primordium of the intraembryonic coelom

Answer 30

Isolated coelomic spaces in the lateral plate & cardiogenic mesoderm, come from intraembryonic coelom

Question 31

endoderm of the umbilical vesicle during head fold

Answer 31

partly incorporated as the | foregut

Question 32

Tail Fold

Answer 32

Folding of the caudal end of the embryo is due to growth of the distal neural tube The caudal eminence (tail region) projects over the cloacal membrane

Question 33

Hindgut during tailfold

Answer 33

Part of the endoderm will form hindgut (descending colon/rectum) Terminal hindgut dilates to form the cloaca (rudiment of urinary bladder/rectum)

Question 34

Before folding primitive streak lies cranial to cloacal | membrane , and after?

Answer 34

after folding, it lies caudal

Question 35

After tail fold:

Answer 35

``` Allantois (diverticulum of umbilical vesicle) is partially incorporated ``` ``` Primitive streak now caudal to cloacal membrane ``` Connecting stalk (umbilical cord primordium) attached to ventral surface

Question 36

During lateral fold:

Answer 36

Abdominal wall forms & incorporates endoderm to form the midgut (SI primordium) Connection btwn umbilical vesicle & midgut is reduced, forming the omphaloenteric duct As umbilical cord forms, communica tion btwn the intraembryonic & extraembryonic coelomic cavities narrows Amniotic cavity expands, obliterates most of extraembryonic coelom Amnion forms epithelial covering of umbilical cord

Question 37

pericardioperitoneal | canals

Answer 37

located dorsal to the foregut, opening of pericardial cavity

Question 38

dorsal mesentery

Answer 38

After embryonic folding, caudal part of foregut, midgut, & hindgut are suspended in the peritoneal cavity from dorsal abdominal wall by this

Question 39

Head fold movements reshape the intraembryonic coelom:

Answer 39

Pericardial cavity now located cranially to septum transversum Heart repositions & bulges into pericardial cavity Two pericardioperitoneal canals lie dorsal to septum transversum Caudal peritoneal cavity is positioned where IE & EE coeloms are continuous

Question 40

Growth of primordial lungs into the pericardioperitoneal canals produces a pair of membranous ridges:

Answer 40

• Pleuropericardial folds (cranial), located superior to the developing lungs • Pleuroperitoneal folds (caudal), located inferior to the lungs

Question 41

Pleuropericardial Membranes

Answer 41

Membranes fuse with mesenchyme ventral to esophagus Separates pericardial cavity from pleural cavities

Question 42

Completing closure process of Pleuroperitoneal Membranes

Answer 42

Myoblasts migrate into the pleuroperitoneal membranes & completes closure process Pleuroperitoneal opening on the right closes slightly before the left

Question 43

Dorsal mesentery

Answer 43

median portion of | diaphragm

Question 44

Myoblasts

Answer 44

grow into the dorsal mesentery | → crura of the diaphragm