Small and Large Intestines

What are the 3 sections of the small intestine

• Duodenum

• Jejunum

• Ileum

What is the general function of small intestine?

For digestion and absorption

Histological Features of Small Intestine

• Does it have villi and why

• What secretes digestive enzyme

• What are enterocytes

• What secretes mucus

Does it have villi and why: Yes, to increase surface area for absorption

What secretes digestive enzyme: Crypts of Lieberkun

What are enterocytes: Absorptive cells

What secretes mucus: Goblet cells

Duodenum

• What

• Location

• Describe its mesentery

• Cranial part closely related to

  • Forming

• Attach to, by

• Function

What: First part of small intestine

Location: Extend from pylorus to beginning of jejunum

Describe its mesentery: Short except in carnivores

Cranial part closely related to: Liver and pancreas

• Forming: Sigmoid loop in horse, ruminants and pigs

Attach to: Liver by hepatoduodenal ligament

Function: Receives bile ducts and pancreatic ducts

Jejunum

• Characteristic

• Describe its mesentery

• In carnivores

  • Occupies

  • Covered by

  • Lies against

• In ruminants

  • Location

Characteristic: Longest part, usually empty

Describe its mesentery: Long, allowing great range especially in carnivores and horse

In carnivores:

• Occupies ventral part of abdominal cavity

• Covered by greater omentum

• Lies against lateral and ventral abdominal wall

In ruminants:

• Intestines entirely to the right

Ileum

• What

• Suspended by

• Attached to

  • By

• Terminates at

What: Short terminal part connecting to large intestine

Suspended by: Caudal part of mesentery (mesoileum)

Attached to: Cecum

• By: Ielocecal fold

Terminates at: Ceococolic junction forming ileal orifice

What are the 4 structures of the large intestine?

• Cecum

• Ascending colon

• Descending colon

• Rectum

What is the general function of the large intestine?

Absorbing water and electrolytes and forms feces

Histological Features of Large Intestine

• Does it have villi

• What gives it immune protection

• What produces mucus

• Why does it have a thicker muscularis externa

Does it have villi: No, flat mucosa

What gives it immune protection: Lymphatic nodules

What produces mucus: Goblet cells

Why does it have a thicker muscularis externa: To move solid waste

What are the 4 layers of the large intestine?

• Mucosa

• Submucosa

• Muscularis

• Serosa

Cecum

• What

• General location

• How join to colon

• Describe its length in cat, dog, pig and ruminants

• In

  • Horse

  • Carnivores

  • Pig

What: Initial blind part of large intestine

General location: Right flank (excluding pig)

Join to: Colon at ileal orifice

Describe its length in cat, dog, pig and ruminants:

• Shortest in cats

• Longer in dog, pig and ruminants

In

• Horse: Large and elongated for fermentation

• Carnivores, ruminants and horse: Lies on right side of abdominal cavity

• Pig: Lies on left side

Rectum

• Continues from

• Before ending at short anal canal, it becomes

  • Forming

• Very prominent in

Continues from: Descending colon into pelvic cavity

Before ending at short anal canal, it becomes: Enlarged

• Forming: Ampula recti (stores feces)

Very prominent in: Horse

Anal Canal

• What

• What anal orifice mean

• What type of epithelium is the mucous membrane

• What surrounds the anus

  • Describe them (smooth or striated muscles)

What: Short terminal portion

Anal orifice: Opening of anus

Type of epithelium in mucous membrane: Stratified squamous epithelium

What surrounds the anus: External and internal sphincters

• Internal sphincter: Continuation of circular smooth muscle of rectum

• External sphincter: Striated muscle from the caudal vertebrae, lying superficial to internal sphincter

How does the large intestine differ from the small intestine (3)

• Villi are absent in large intestine

• Microvilli of large intestine are less abundant

• Goblet cells are more prominent

What are these terms:

• Cecocolic junction

• Mesentry

• Heptaoduodenal ligament

• Ampula recti

Cecocolic junction: The junction between cecum and ascending colon

Mesentry: Fold of peritoneum (thin layer of tissue) that attaches to intestines to posterior abdominal wall

Heptaoduodenal ligament: Part of less omentum and connects liver to the duodenum

Ampula recti: Expanded part of rectum

What is the location of the intestines?

From pylorus (last part of stomach) to anus

What is the anal canal?

Short passage at the end of rectum (final part of digestion)

What is the intestinal length for these animals

• Dog

• Horse

• Pig

• Ox

• Small ruminants

Dog: 5x body length

Horse: 10x body length

Pig: 15x body length

Ox: 20x body length

Small ruminants: 25x body length

What are the 3 types of colon?

• Ascending colon

• Transverse colon

• Descending colon

What is the colon like in these animals

• Ruminants, pig and horse

Generally the ascending colon is longer than of carnivores

• Ruminants: Flat, disc shaped coil

• Pig: Cone shaped coil

• Horse: Double on itself twice, forming a large horseshoe-shaped loop

Descending Colon

• In pig

• In horse

• In ruminant

• What is rectum

In pig: Straight colon before rectum

In horse: Elongated and suspended from roof of abdominal cavity by mesentery

In ruminant: Sigmoid flexure at pelvic inlet

What is rectum: Straight terminal part in the pelvic cavity (short anal canal)

Blood Vessels

• Which blood vessels supply:

  • Small intestine

  • Proximal duodenum

  • Large intestine

  • Rectum

• Veins of intestinal tract go to

• Blood from rectum return to

• Which blood vessels supply:

  • Small intestine: Cranial mesenteric artery

  • Proximal duodenum: Celiac artery

  • Large intestine: Cranial and caudal mesenteric artery

  • Rectum: Internal iliac artery

• Veins of intestinal tract go to: Portal vein

• Blood from rectum return to: Caudal vena cava

Innervation

• What does sympathetic innervation cause

• What does parasympathetic innervation cause

• Parasympathetic fibers originates in

What does sympathetic innervation cause: Slowing down activity (retardation)

What does parasympathetic innervation cause: Increases activity

Parasympathetic fibers originates in: Cranial and sacral regions