The Abdomen

Question 1

Define the boundaries of the abdominal cavity

Answer 1

Abdominal cavity, largest hollow space of the body. Its upper boundary is the diaphragm, a sheet of muscle and connective tissue that separates it from the chest cavity; its lower boundary is the upper plane of the pelvic cavity

Question 2

Describe the peritoneal cavity

Answer 2

Peritoneum etymologically means wrapped tightly around, which is a good description of the arrangement of this serous membrane that consists of two parts: the parietal peritoneum that covers the abdominal wall, and the diaphragm and the visceral peritoneum that covers the intraabdominal viscera.

Question 3

Parietal peritoneum

Answer 3

an outer layer which adheres to the anterior and posterior abdominal walls.

Question 4

Visceral peritoneum

Answer 4

an inner layer which lines the abdominal organs. It’s made when parietal peritoneum reflects from the abdominal wall to the viscera.

Question 5

layers of the body wall

Answer 5

There are nine layers to the abdominal wall: skin, subcutaneous tissue, superficial fascia, external oblique muscle, internal oblique muscle, transversus abdominis muscle, transversalis fascia, preperitoneal adipose and areolar tissue, and peritoneum

Question 6

subcutaneous tissue

Answer 6

Subcutaneous tissue, which is also known as the hypodermis, is the innermost layer of skin. It’s made up of fat and connective tissues that house larger blood vessels and nerves, and it acts as an insulator to help regulate body temperature.

Question 7

external oblique muscle

Answer 7

External abdominal oblique is a paired muscle located on the lateral sides of the abdominal wall

Origin: External surfaces of ribs 5-12
Insertion: Linea alba, pubic tubercle, anterior half of iliac crest
Action: Bilateral contraction - Trunk flexion, compresses abdominal viscera, expiration
Unilateral contraction - Trunk lateral flexion (ipsilateral), trunk rotation (contralateral)
Innervation: Motor: Intercostal nerves (T7- T11), Subcostal nerve (T12)
Sensory: Iliohypogastric nerve (L1)
Blood supply: Lower posterior intercostal arteries, subcostal artery, deep circumflex iliac artery
Fibers run cauldial dorsal

Question 8

transversalis fascia

Answer 8

The transversalis fascia (or transverse fascia) is a thin aponeurotic membrane which lies between the inner surface of the transverse abdominal muscle and the parietal peritoneum.

Question 9

preperitoneal adipose

Answer 9

Preperitoneal refers to adipose tissue between the parietal peritoneum and the abdominal wall.

Question 10

areolar tissue

Answer 10

Areolar connective tissue is one of six forms of connective tissue within the body and is named after the airy appearance of the tissue. It is found surrounding blood vessels, nerve bundles, muscles, and organs. It also fills the spaces between organs and connects your skin to your underlying muscle.

Question 11

peritoneum

Answer 11

The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesothelium supported by a thin layer of connective tissue.

• Serous membrane, secretes serous fluid
• Envelopes viscera (intraperitoneal or retroperitoneal)
• Protective

Question 12

serous membrane

Answer 12

serous membrane (or serosa) is a smooth tissue membrane consisting of two layers of mesothelium, which secrete serous fluid. The inner layer that covers organs (viscera) in body cavities is called the visceral membrane.

Question 13

Abdominal Cavity

Answer 13

• Diapragm
• Body wall, laterally and
ventrally
 • Pelvis
• Dorsal body wall

Question 14

Internal Abdominal Oblique

Answer 14

Internal abdominal oblique is a broad thin muscular sheet found on the lateral side of the abdomen.

As its name suggests, the direction of its fibers are obliquely oriented, perpendicular to those of the external abdominal oblique. Together with the other abdominal muscles, the internal abdominal oblique is important for movements of the trunk, maintaining normal abdominal tension, and increasing intra-abdominal pressure.

Origin: Anterior two-thirds of iliac crest, iliopectineal arch, thoracolumbar
fascia
Insertion: Inferior borders of ribs 10-12, linea alba, pubic crest & pectin pubis (via conjoint tendon)
Action: Bilateral contraction - Trunk flexion, compresses abdominal viscera, expiration
Unilateral contraction - Trunk lateral flexion (ipsilateral), trunk rotation (ipsilateral)
Innervation: Intercostal nerves (T7-T11), subcostal nerve (T12), iliohypogastric nerve (L1), ilioinguinal nerve (L1)
Blood supply: Lower posterior intercostal and subcostal arteries, superior and inferior epigastric arteries, superficial and deep circumflex arteries,posterior lumbar arteries

Question 15

Transversus abdominis muscle

Answer 15

The transversus abdominis is a broad paired muscular sheet found on the lateral sides of the abdominal wall.

As its name suggests, the fibers of transversus abdominis are oriented transversely, perpendicular to the linea alba. Together with the other abdominal muscles, transversus abdominis is important for maintaining normal abdominal tension and increasing intra-abdominal pressure.

Origin: Internal surfaces of costal cartilages of ribs 7-12, thoracolumbar fascia, anterior two thirds of iliac crest, iliopectineal arch
Insertion: Linea alba, aponeurosis of internal abdominal oblique muscle; pubic crest, pectinal line of pubis
Action: Bilateral contraction - Compresses abdominal viscera, expiration
Unilateral contraction - Trunk rotation (ipsilateral)
Innervation: Intercostal nerves (T7-T11), subcostal nerve (T12), iliohypogastric nerve (L1), ilioinguinal nerve (L1)
Blood supply: Lower posterior intercostal and subcostal arteries, superior and inferior epigastric arteries, superficial and deep circumflex arteries,posterior lumbar arteries

Question 16

Rectus Abdominis

Answer 16

Rectus abdominis, informally known as the abs muscle, is a long muscle of the anterior abdominal wall.

Origin: Pubic symphysis, pubic crest
Insertion: Xiphoid process, costal cartilages of ribs 5-7
Innervation: Intercostal nerves (T7-T11), subcostal nerve (T12)
Blood supply: Inferior epigastric and superior epigastric arteries; contributions from posterior intercostal, subcostal and deep circumflex arteries
Function: Trunk flexion, compresses abdominal viscera, expiration

Question 17

External inguinal ring

Answer 17

The superficial or external ring is the terminal end of the inguinal canal. It is located just superior to the pubic tubercle. The superficial ring has a triangular shape that is made by fibers of the external oblique muscle. These fibers continue to cover the inguinal contents as they descend into the scrotal area

Question 18

inguinal canal

Answer 18

there are numerous openings that allow structures to pass from one area to another. They are referred to by different names, such as foramina, canals, or hiatus. The anterior abdominal wall – which extends in a craniocaudal fashion from the xiphisternum and adjacent lower borders of the lower eight ribs to the inguinal ligaments and the pubis – has naturally occurring paired canals in the lower regions known as the inguinal canals. More specifically, the inguinal canals are found in the inguinal region, which extend from the lower abdomen into the medial part of the proximal thighs on each side.

The oblique tunnels serve as a conduit that allows passage of the male gonads from their intra-abdominal point of origin to the final destination in the scrotal sac. The boundaries of this hiatus are formed by the muscles of the anterior abdominal wall in the left and right iliac fossa. The size of the canals increase with age and are significantly more developed in males than in females.

Question 19

Stomach

Answer 19

The stomach is a muscular organ located on the left side of the upper abdomen. The stomach receives food from the esophagus. As food reaches the end of the esophagus

Parts: Cardia, fundus, body, pyloric part
Mnemonic: Cows Find Bulls Passionate

the stomach spans the region between the cardiac and pyloric orifices of the gastrointestinal tract. It is covered and connected to other organs by peritoneum. The lesser omentum connects the stomach to the liver and then extends around the stomach. The greater omentum then continues inferiorly from the stomach, hanging from it like a curtain

The mucosa has a wrinkled aspect, consisting of ridges called gastric folds, or rugae. During distension of the organ, the gastric folds disappear. Along the lesser curvature of the stomach, a temporary, continuous furrow called gastric canal is formed between the gastric folds. This facilitates the passage of saliva and fluids during swallowing.

Functions : Mechanical and chemical digestion, absorption, hormone secretion
Layers: Mucosa, submucosa, muscularis externa and serosa
Mnemonic: M.S.M.S
Blood supply: Gastric arteries, gastroomental arteries, short gastric arteries, posterior gastric arteries, gastroduodenal artery
Innervation
Parasympathetic: vagus nerve (CN X)
Sympathetic: celiac plexus (T5-T12)
Lymphatics: Gastric, gastroomental, and pyloric lymph nodes

Question 20

Intestines

Answer 20

The small intestine has three parts. The first part is called the duodenum. The jejunum is in the middle and the ileum is at the end. The large intestine includes the appendix, cecum, colon, and rectum.

Question 21

duodenum

Answer 21

The duodenum is the first part of the small intestine. It is located between the stomach and the middle part of the small intestine, or jejunum. After foods mix with stomach acid, they move into the duodenum, where they mix with bile from the gallbladder and digestive juices from the pancreas

Question 22

jejunum

Answer 22

The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialized for the absorption by enterocytes of small nutrient molecules which have been previously digested by enzymes in the duodenum.

Question 23

ileum

Answer 23

The ileum (/ˈɪliəm/) is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds.

At the distal end, the ileum is separated from the large intestine, into which it opens, by the ileocecal valve. The ileum itself is very rich in lymphoid follicles and is attached to the abdominal wall by the mesentery. Its vascular supply is provided by the ileal arteries and its innervation via the coeliac and superior mesenteric plexi.

In terms of histology, the mucosa of the ileum consists of simple columnar epithelium comprising of enterocytes and goblet cells. A characteristic histological feature of the ileum are Peyer’s patches

The transition from the jejunum to the ileum is not sharply marked

Question 24

cecum

Answer 24

The cecum or caecum is a pouch within the peritoneum that is considered to be the beginning of the large intestine. It is typically located on the right side of the body

The ileocaecal valve (Fig. 4.39) at the termination of the ileum is located on the left side at the junction between the caecum and the ascending colon

Question 25

colon

Answer 25

The colon (large intestine) is the distal part of the gastrointestinal tract, extending from the cecum to the anal canal. It receives digested food from the small intestine, from which it absorbs water and electrolytes to form faeces.

Anatomically, the colon can be divided into four parts – ascending, transverse, descending and sigmoid. These sections form an arch, which encircles the small intestine.

Question 26

Ascending Colon

Answer 26

The colon begins as the ascending colon, a retroperitoneal structure which ascends superiorly from the cecum.

When it meets the right lobe of the liver, it turns 90 degrees to move horizontally. This turn is known as the right colic flexure (or hepatic flexure), and marks the start of the transverse colon

Question 27

Transverse Colon

Answer 27

The transverse colon extends from the right colic flexure to the spleen, where it turns another 90 degrees to point inferiorly. This turn is known as the left colic flexure (or splenic flexure). Here, the colon is attached to the diaphragm by the phrenicocolic ligament.

The transverse colon is the least fixed part of the colon, and is variable in position (it can dip into the pelvis in tall, thin individuals). Unlike the ascending and descending colon, the transverse colon is intraperitoneal and is enclosed by the transverse mesocolon.

Question 28

Descending Colon

Answer 28

After the left colic flexure, the colon moves inferiorly towards the pelvis – and is called the descending colon. It is retroperitoneal in the majority of individuals, but is located anteriorly to the left kidney, passing over its lateral border.

When the colon begins to turn medially, it becomes the sigmoid colon.

Question 29

Sigmoid Colon

Answer 29

The 40cm long sigmoid colon is located in the left lower quadrant of the abdomen, extending from the left iliac fossa to the level of the S3 vertebra. This journey gives the sigmoid colon its characteristic “S” shape.

The sigmoid colon is attached to the posterior pelvic wall by a mesentery – the sigmoid mesocolon. The long length of the mesentery permits this part of the colon to be particularly mobile.

Question 30

rectum

Answer 30

The rectum is a chamber that begins at the end of the large intestine, immediately following the sigmoid colon, and ends at the anus (see also Overview of the Anus and Rectum). Ordinarily, the rectum is empty because stool is stored higher in the descending colon.