Digestive 3

Question 1

1. Teniae coli - large intestine

Answer 1

• Three longitundinal strips spaced equally around large intestine.
• Thickenings of longitudinal layer of muscularis externa.
• Shorter in length than large intestine, causing intestine to “pucker” into sacs called Haustra.

Question 2

2. Haustra - large intestine

Answer 2

“Sacs” of intestine

Question 3

3. Epiploic appendages - large intestine

Answer 3

• Fat filled pouches.

* Unknown function.

Question 4

Cecum - large intestine

Answer 4

• Blind intestinal pouch in bottom right corner of abdomen.
• Receives contents from ileum.
• Ileocecal valve: sphincter which stops reflux of feces back into ileum.

Question 5

Appendix - large intestine

Answer 5

• Vermiform “worm-like”.
• Vestigial organ? Or safe haven for beneficial gut bacteria? Can repopulate gut after diarrhea flushes
out gut flora.
• Lots of lymphoid tissue.

Question 6

Appendicitis

Answer 6

Acute inflammation of the appendix.
• Results from a blockage that traps infectious bacteria in the lumen of the appendix.
• Blockage caused by feces, or by pathogen (virus)-induced swelling of lymphoid tissue in appendix walls.

Question 7

Colon

Answer 7

• Ascending Colon
• Non-motile; connects cecum to transverse colon
• Transverse Colon
• Largest, most superior, and most motile part of large intestine
• Descending Colon
• Non-motile; connects transverse colon to sigmoid colon.
• Sigmoid Colon (S-shaped)
• Very motile, connects descending colon to rectum.

Two flexures:
• Right colic (hepatic) flexure
• Left colic (splenic) flexure

Question 8

Colon: Histology

Answer 8

Mucosa:
• Relatively smooth - no plica circulares or villi, reflecting fewer nutrients absorbed. Large
crypts are present.
• Colonocytes - absorb water and electrolytes.
• Goblet cells – very abundant, secrete mucus to ease passage of feces.
Submucosa:
• Thin, typical connective tissue, some lymphoid tissue.
Muscularis externa:
• Inner circular and outer longitudinal layers.
• Thin except at teniae coli – thickenings of longitudinal layer of muscularis externa.
Serosa:
• Contains epiploic appendages – fat filled pouches.
Unknown significance.

Question 9

Colonocytes

Answer 9

absorb water and electrolytes.

Question 10

Goblet cells

Answer 10

very abundant, secrete mucus to ease passage of feces.

Question 11

Diverticulosis

Answer 11

Formation of multiple sacs called diverticula – small herniations of
mucosa through colon wall. Most frequent in sigmoid colon.
• Diet lacks fiber à reduced fecal volume à circular muscle exerting greater pressure on the colon walls à diverticula.
• If diverticula become infected and or perforate à diverticulitis.

Question 12

Ulcerative Colitis

Answer 12

Subtype of inflammatory bowel disease.
• Inflammation of the large intestine mucosa.
• Abnormal immune response to bacterial antigens that normally occur in intestine.

Question 13

Rectum

Answer 13

• Fixed (immotile) portion of large intestine distal to sigmoid colon.
• No teniae coli.
• Thick, well-developed longitudinal muscles that help promote defecation.
• Internally, contains three transverse rectal folds that aid continence and
prevent feces from being passed
along with flatus (gas).

Question 14

Anal canal

Answer 14

• Terminal end of large intestine continuous with rectum.
• Internally, divided by the pectinate line.
• Only 3 cm long.
• Begins at end of levator ani (main pelvic floor muscle) and ends at anus.

Question 15

Superior to pectinate line:

Answer 15

• Visceral sensory nerves; insensitive to pain.
• Continuous blood supply with GI tract.

• Anal columns: longitudinal folds of mucosa.
• Anal valves: connect adjacent anal columns.
• Anal sinuses: pockets formed by valves. Filled with mucus, which is released when sinuses are
compressed during defecation.

Question 16

Inferior to pectinate line:

Answer 16

• Somatic sensory nerves; sensitive to pain.

* Distinct blood supply from rest of GI tract.

Question 17

Anal Canal - Sphincters

Answer 17

The wall of the anal canal contains two sphincter muscles. Both act to feces from leaking from the anus betweendefecations and during emotional stress:

Question 18

Internal anal sphincter

Answer 18

• Involuntary smooth muscle that surrounds the anal canal.
• Thickening of the circular layer of the muscularis externa.
• Tonic state of contraction, controls release of feces from the rectum during defecation.

Question 19

External anal sphincter

Answer 19

• Voluntary skeletal muscle that surrounds anal canal.
• In tonic state of contraction.
• During potty training, children learn how to control this muscle.

Question 20

Defecation

Answer 20

1. Mass peristaltic movements squeeze feces into rectum, stretching rectal wall, triggering defecation reflex.
2. Walls of sigmoid colon and rectum contract. Internal sphincter relaxes.
3. Voluntary relaxation of external anal sphincter? YES!
4. Voluntary contraction of the diaphragm and abdominal muscles increase pressure.
5. Feces expelled.

Question 21

Arterial supply

Answer 21

Three anterior (unpaired)
branches of the abdominal aorta:

Question 22

Celiac trunk

Answer 22

• Stomach, proximal half of duodenum

- Liver and spleen

Question 23

Superior mesenteric artery

Answer 23

• Distal half of duodenum
• Jejunum, ileum, cecum/appendix
• Ascending colon, 2/3 of transverse colon

Question 24

Inferior mesenteric artery

Answer 24

• Distal 1/3 of transverse colon
• Descending and sigmoid colon
• Rectum and anal canal (above pectinate line)
• *Anal canal below pectinate line is supplied by inferior rectal artery.

Question 25

Hepatic portal system

Answer 25

carries absorbed nutrients from alimentary tract directly to liver where poisons and drugs can be detoxified, before traveling to heart.
Tributaries:
- Splenic vein
- Superior mesenteric vein
- Inferior mesenteric vein

Question 26

Visceral Peritoneum

Answer 26

covers the external surfaces of organs (serosa).

Question 27

Parietal Peritoneum

Answer 27

lines body wall; continuous with visceral peritoneum.

Question 28

Peritoneal Cavity

Answer 28

potential space between visceral and parietal peritoneum. Contains a small amount of fluid.

Question 29

Mesentery:

Answer 29

• Double layer of peritoneum

* Connects intraperitoneal organs with each other, or to abdominal wall.

Question 30

Intraperitoneal organs:

Answer 30

• Almost completely surrounded by peritoneum.
• Organ is freely movable.
• e.g. stomach, jejunum, ileum, transverse colon, sigmoid colon.

Question 31

Retroperitoneal organs:

Answer 31

• Organ is behind peritoneum; only part is covered by peritoneum.
• Organ is fixed in position.
• e.g. duodenum, pancreas, ascending/descending colon.

Question 32

Mesenteries

Answer 32

double layer of peritoneum fused together

Function: anchor organs in place, store fat, and provide a route for blood vessels and nerves to reach organs.

Question 33

1. Ventral mesenteries

Answer 33

Extend from anterior abdominal wall to stomach and liver.

1. Falciform ligament – binds liver to anterior abdominal wall and diaphragm.
2. Lesser omentum – runs from liver to lesser curvature of the stomach

Question 34

2. Dorsal mesenteries

Answer 34

Extend from posterior abdominal wall to alimentary canal.
1. Greater omentum
• Connects greater curvature of stomach to transverse colon.
• Elongated anteriorly, covers the transverse colon and small intestine like an apron.
2. Mesentery – Supports the jejunum and ileum.
• Fans inferiorly from posterior abdominal wall like a pleated curtain.
3. Transverse mesocolon – Connects transverse colon to posterior abdominal wall. Fused to underside of
greater omentum.
4. Sigmoid mesocolon – Connects the sigmoid colon to the posterior pelvic wall.

Question 35

Abdominopelvic Cavity

Answer 35

Clinical Application: Bowel sounds convey valuable information about intestinal health. Clinicians will listen with a stethoscope in each of the four quadrants. Normal bowl sounds: high pitched gurgles every 5-15 seconds. Less frequent: halt in intestinal activity. Loud sounds may indicate inflammation, diarrhea, or other bowel disorder.