Understanding the peritoneal cavity

Question 1

what is the peritoneal cavity’s origin

Answer 1

Origin of the gut

The embryo – gastrula – the stage following the blastula, embryo develops 3 layers ecto, endo and mesoderm

Question 2

what forms the peritoneal cavity

Answer 2

Endoderm – majority of the gut, including most of epithelium and glands of digestive tract
Mesoderm – muscular layers
Ectoderm – epithelium at extremities of tract (cranial and caudal)

Question 3

how is the primitive gut formed

Answer 3

Formed as a result of two folds
Cranial-caudal (head to tail) and lateral (side to side)
At 4 weeks the cranial and caudal ends still closed by membranes, bucco-pharyngeal (cranial) and cloacal (caudal)

Question 4

what are gut divisions and what do they become

Answer 4

Foregut – oesophagus, stomach, proximal half duodenum, liver, pancreas
Midgut- distal half duodenum, jejunum, ileum, cecum, ascending and ¾ transverse colon
Hindgut – ¼ transverse, descending and sigmoid colon and rectum

Question 5

what are mesenteries

Answer 5

hold primitive gut in place
of mesodermal origin
formed by double layer of peritoneum, dorsal or ventral according to relative position in respect to gut (visceral and parietal peritoneum attached by mesenteries)

Question 6

what do mesenteries do

Answer 6

suspends intestines
pathway for blood, innervation, lymphatics to reach gut
ventral mesentery degenerates during development, except foregut

Question 7

what happens to the gut in development

Answer 7

folds

Question 8

what can result from incorrect folding

Answer 8

cause unclear 
Format – duodenum constriction
Midgut volvulus, leading to ischaemia, necrosis or possibly death
Common symptoms 
Vomiting, pain, abdominal distension

Question 9

what is the dorsal mesentery

Answer 9

Attaches gut organs to posterior abdominal wall

Gives rise to gastrophrenic ligament, lienorenal ligament, greater omentum, mesentery of small and large intestine

Question 10

what is the ventral mesentery

Answer 10

At foregut region only, gives rise to ligaments around liver, falciform ligament, lesser omentum
Lesser omentum – attaches lesser curvature stomach to back of liver and has a free edge

Question 11

where is the abdomen located

Answer 11

Below diaphragm
Abdominal cavity occasionally called abdominopelvic (abdomen proper + greater pelvis)
Greater pelvis continuous with lesser pelvis

Question 12

what is the inguinal ligament

Answer 12

attach ASIS to pubic tubercle on iliac bone (pelvis)

Question 13

what muscles make up the abdominal wall

Answer 13

Flat abdominal muscles

Lumbar vertebral column

Question 14

what are the muscles of the anterior abdominal wall

Answer 14

external and internal oblique
transverse abdominis
rectus abdominis

Question 15

where is the external oblique

Answer 15

from outer surface of lower 8 ribs to linea alba, iliac crest and public tubercle

Question 16

where is the internal oblique

Answer 16

from lateral 1/3 inguinal ligament, anterior 2/3 of iliac crest to linea alba, costal margin, crest of pubic bone

Question 17

where is the transverse abdominis

Answer 17

from lateral 1/3 inguinal ligament, internal surface of lower 6 ribs, iliac crest to linea alba and crest of pubic bone

Question 18

where is the rectus abdominis

Answer 18

from public symphysis and crest to xiphoid process, 5th-7th costal cartilages

Question 19

what is the blood supply and innervation of the muscles of the anterior abdominal wall

Answer 19

Arteries – sup and inf epigastric, intercostal, circumflex iliac
Veins – thoracoepigastric (between lat thoracic and sup epigastric)
Innervation
Thoracoabdominal nerves (also thoracic and subcostal nerves for rectus abdominis)

Question 20

what is the function of the muscles of the muscles of the anterior abdominal wall

Answer 20

Ext oblique work with int oblique for torsional movement of trunk
Int oblique – flex and rotate trunk, compress viscera
Transverse abdominus – compress and support viscera
Rectus abdominis – flex trunk, compress viscera

Question 21

what are the greater and lesser sacs

Answer 21

Formed as a result of organ rotation
Lesser sac behind stomach
Rest of peritoneal cavity – greater sac
Communicate via epiphonic foramen (of winslow)

Question 22

what does the inguinal canal do

Answer 22

Serves as a passageway for the spermatic cord to reach scrotum of male and the round ligament of the uterus to reach labia majora in the female
Limited by the superficial and deep inguinal rings

Question 23

what also runs in the inguinal canal cavity

Answer 23

For both genders the genital nerve (a branch from the genitofemoral) and other blood and lymphatic vessels also travel through this canal
The inguinal canal is considerably larger in males, compared to females

Question 24

what does the spermatic cord consist of

Answer 24

vas deferens, gonadal vessels, nerves, lymphatics, cremaster muscle

Question 25

what happens to the spermatic cord as it passes through the abdominal wall

Answer 25

it takes a sleeve or covering from each of the 3 layers
Transversalis fascia – contributes the innermost covering of the spermatic cord – internal spermatic fascia
Internal oblique – contributes the middle covering layer – the cremasteric fascia
External oblique – the outer covering – the external spermatic fascia