Digestion anatomy

Anatomy Digestive systemAnatomy Digestive system

Organs of the Digestive SystemOrgans of the Digestive System

Two main groups Alimentary canal or gastrointestinal tract –

continuous coiled hollow tube from mouth to anus(5-7 meter)

Accessory digestive organs: teeth ,tongue ,salivary gland ,liver ,gallbladder ,and pancreas

Organs of the Digestive SystemOrgans of the Digestive System

Organs of the Alimentary CanalOrgans of the Alimentary Canal

Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus

Layers of Alimentary Canal OrgansLayers of Alimentary Canal Organs Mucosa

Innermost layer Moist membrane

1. Surface epithelium : secretion and absorbtion,renew every 5-7 days also contain enteroendocrine cells

2. Small amount of connective tissue (lamina propria): contain blood and lymphatic vessele also contain MALT

3. Small smooth muscle layer

Layers of Alimentary Canal OrgansLayers of Alimentary Canal Organs

Submucosa Just beneath the mucosa Soft connective tissue with blood vessels,

nerve endings, and lymphatics also contain submucosal plexus


Muscularis externa – smooth muscle

1. Inner circular layer

2. Outer longitudinal layer

Between them is myenteric plexus

Serosa Outermost layer – visceral peritoneum Layer of serous fluid-producing cells

(mesothelium)

• A thin membrane (the peritoneum) lines the walls of the abdominal cavity and covers much of the viscera.

• The parietal peritoneum lines the walls of the cavity and the visceral peritoneum covers the viscera.

• Between the parietal and visceral layers of peritoneum is a potential space (the peritoneal cavity).

• The peritoneal cavity is subdivided further into The greater sac The omental bursa .

PeritoneumPeritoneum

PeritoneumPeritoneum

• The omenta consist of two layers of peritoneum, which pass from the stomach and the first part of the duodenum to other viscera. There are two:

The greater omentum

The lesser omentum

OmentumOmentum

OmentumOmentum

Mesenteries are peritoneal folds that attach viscera to the posterior abdominal wall. They allow some movement and provide a conduit for vessels, nerves, and lymphatics to reach the viscera and include: •the mesentery-associated with parts of the small intestine;•the transverse mesocolon-associated with the transverse colon;•the sigmoid mesocolon-associated with the sigmoid colon.

MesentriesMesentries

MesentriesMesentries

EsophagusEsophagus The esophagus is a muscular, collapsible tube

about 25 cm long that joins the pharynx to the stomach.

The esophagus enters the abdomen through an opening in the right crus of the diaphragm

Passageway for food only (respiratory system branches off after the pharynx)

Conducts food by peristalsis

• The upper third is skeletal muscle (voluntary), middle third is mixed, and lower third is smooth muscle (involuntary).

• esophagogastric junction is located approximately at the level of the diaphragm. Contractions of the diaphragm create sphincter-like effects, preventing reflux of stomach acids and content. The esophagogastric junction is a functional, not anatomical, sphincter.

EsophagusEsophagus

Stomach AnatomyStomach Anatomy

Located on the left side of the abdominal cavity

Food enters at the cardioesophageal sphincter

• It is roughly J-shaped and has two openings, the cardiac and pyloric


Regions of the stomach Cardiac region – near the heart Fundus Body Phylorus – funnel shaped terminal end


Other features of the stomach include: The greater curvature The lesser curvature The cardial notch The angular incisure

Small IntestineSmall Intestine

The small intestine is the longest part of the gastrointestinal tract and extends from the pyloric orifice of the stomach to the ileocecal fold.

This hollow tube, which is approximately 6-7 m long with a narrowing diameter from beginning to end .

Subdivisions of the Small IntestineSubdivisions of the Small Intestine

Duodenum(25cm) Attached to the stomach Curves around the head of the pancreas Fixed retroperitoneal structure

Jejunum (2.5m) Attaches anteriorly to the duodenum

Ileum (3.5m) Extends from jejunum to large intestine

Large IntestineLarge Intestine

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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The large intestine extends from the distal end of the ileum to the anus, a distance of approximately 1.5 m.

It absorbs fluids and salts from the gut contents, thus forming feces.

Larger in diameter, but shorter than the small intestine

Frames the internal abdomen

Structures of the Large IntestineStructures of the Large Intestine

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Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Cecum Colon

Ascending Transverse Descending S-shaped sigmoidal

Rectum Anus – external body opening

The digestive system is supplied by the celiac artery. The celiac artery is the first major branch from the abdominal aorta.

There are three main divisions – the left gastric artery, the common hepatic artery and the splenic artery.

The celiac artery supplies the liver, stomach, spleen and the upper halves of the duodenum and the pancreas with

oxygenated blood .

Most of the blood is returned to the liver via the portal venous system for further processing and detoxification before returning to the systemic circulation via the hepatic portal vein.

Blood supply

InnervationThe enteric nervous system consists of some one hundred million neurons that are embedded in the peritoneum, the lining of the gastrointestinal tract extending from the oesophagus to the anus.

These neurons are collected into two plexuses - the myenteric (or Auerbach's) plexus that lies between the longitudinal and the smooth muscle layers, and the submucosal (or Meissner's) plexus that lies between the circular smooth muscle layer and the mucosa.

Parasympathetic innervation to the ascending colon is supplied by the vagus nerve. Sympathetic innervation is supplied by the splanchnic nerves that join the celiac ganglia. Most of the digestive tract is innervated by the two large celiac ganglia, with the upper part of each ganglion joined by the greater splanchnic nerve and the lower parts joined by the lesser splanchnic nerve. It is from these ganglia that many of the gastric plexuses arise.

Digestion anatomy

Science

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