Peritoneal Cavity

Question 1

Background

Answer 1

The embryo: gastrula - the stage following the blastula, the embryo develops 3 layers (ecto, meso and endoderm)
Endoderm: majority of gut, including most of epithelium and glands of digestive tract
Mesoderm: muscular layer
Ectoderm: epithelium at extremities of tract (cranial and caudal)

Question 2

The primitive gut

Answer 2

Formed as a result of 2 folds (cranial-caudal and lateral)
After 4 weeks, the cranial and caudal ends are still closed by membranes (bucco-pharyngeal and cloacal)
Held in position by mesenteries (a structure of mesodermal origin)

Question 3

Gut division

Answer 3

Foregut: oesophagus, stomach, proximal half of duodenum, liver, pancreas.
Midgut: distal half of duodenum, jejunum, ileum, cecum, ascending and 3/4 of transverse colon
Hindgut: 1/4 of transverse, descending and sigmoid colon, and rectum

Question 4

Peritoneum and Mesentery

Answer 4

Mesentery: formed by a double layer of peritoneum (parietal and visceral); dorsal or ventral according to its relative position with respect to gut tube
Mesentery suspends intestines
It is a pathway for blood, innervation and lymphatics to reach the gut
Ventral mesentery degenerates during development, except for foregut

Question 5

Anomaly of Gut Rotation

Answer 5

Cause is unclear
Format: duodenum constriction; midgut volvulus, leading to ischaemia, necrosis or possibly death; common symptoms including vomiting pain and abdominal distention

Question 6

Dorsal and Ventral Mesentery

Answer 6

Dorsal: Attaches gut organs to posterior abdominal wall
Gives rise to gastrosplenic ligament, lienorenal ligament, greater omentum, mesentery of s and l intestine
Ventral: At foregut region, it gives rise to ligaments around the liver, falciform ligament, lesser omentum
(Lesser omentum attaches lesser curvature stomach to back of liver, has a free edge)

Question 7

External Oblique

Answer 7

From outer surface of lower eight ribs to linea alba, iliac crest and pubic tubercle
Function: work with internal oblique for torsional movement of trunk

Question 8

Internal Oblique

Answer 8

From lateral 1/3 of inguinal ligament and anterion 2/3 of iliac crest, to linea alba, costal margin, crest of pubic bone
Function: flex and rotate trunk; compress viscera

Question 9

Transverse Abdominis

Answer 9

From lateral 1/3 of inguinal ligament and interior surface lower 6 ribs & iliac crest to linea alba and crest of pubic bone
Function: compress and support viscera

Question 10

Rectus Abdominis

Answer 10

From pubic symphysis & crest to xyphoid process, 5-7th costal cartilages
Function: flexes trunk, compress viscera

Question 11

Muscles of the Anterior Abdominal Wall

Answer 11

Blood supply/drainage:
Arteries - superior and inferior epigastric, intercostal, circumflex iliac
Veins - thoracoepigastric
Innervation:
Thoracoabdominal nerves (also thoracic and subcostal nerves for rectus abdominis)

Question 12

Lesser/Greater Sacs

Answer 12

Formed as a result of organ rotation
Lesser sac behind stomach
Greater sac - rest of peritoneal cavity
Communicate via the epiploic foramen (of Winslow)

Question 13

Inguinal Canal

Answer 13

Serves as a passageway for: the spermatic cord to react the scrotum in the male, & the round ligament of the uterus to reach the labia majora in the female
Limited by the superficial and deep inguinal rings
For both genders the genital nerve (a branch of the genitogemoral) and other blood and lymphatic vessels also travel through this canal
The inguinal canal is considerably larger in males, compared with females

Question 14

The Spermatic Cord

Answer 14

The spermatic cord consists of: vas deferens, gonadal vessels, nerves, lymphatics and cremaster muscle
As the spermatic cord passes through abdominal wall, it takes a sleeve or covering from each of the 3 layers
Transversalis fascia (innermost covering - internal spermatic fascia)
Internal oblique (middle layer covering of cord - cremasteric fascia)
External Oblique (outer covering - external spermatic fascia)