Health Care: Gastrointestinal and Hepatobiliary System

Topics: Digestion, Stomach, Liver Pages: 18 (3207 words) Published: January 19, 2013
Gastrointestinal and Hepatobiliary System
I. Structure and Organization
A. Divisions (tract tube from mouth to rectum)
1. Upper (mouth, esophagus, stomach) – intake
2. Middle (small intestine – duodenum, jejunum, ileum) – digestion 3. Lower (cecum, colon, rectum) – storage & elimination channel 4. Accessory organs (salivary glands, liver, pancreas) – juices for dismantle, use, & storage of food B. Functions of the GI tract

1. Ingestion
2. Mechanical processing
3. Digestion
4. Secretion
5. Absorption
6. Excretion
C. Histological Organization
1. Mucosa = inner lining
a. Epithelial surface with glandular secretion & connective tissue lining * Mucosal folds – increases surface area for expansion & absorption * Villi – fingerlike projections in small intestine – increase surface area b. Cells of mucosa = columnar epithelium with secretory cells c. Muscularis mucosae = band of smooth muscle & elastic fibers 2. Submucosa – loose connective tissue around muscularis mucosae a. Contains blood vessels & lymphatic vessels & nerves b. Submucosal plexus = neural tissue for smooth muscle movement & glandular secretions 3. Muscularis Externa – smooth muscle in circular & longitudinal pattern a. Mixing and movement function

b. Autonomic reflex of myenteric plexus
* Parasympathetic
* Sympathetic
4. Serosa – serous membrane over the muscularis externa a. Visceral peritoneum lines peritoneal organs
b. Parietal peritoneum line abdominal wall
c. Mesenteries – loose connective tissue connects visceral & parietal * Contains access route for blood, nerves & lymph
* Suspends jejunum & ileum – double folded
* Attached to dorsal abdominal wall = fan shaped
* Greater omentum = double fold of peritoneal membrane
* Extend from stomach, covering transverse colon & intestines- helps control infection spread * Lesser omentum – between transverse fissure liver & lesser curve stomach D. Movement of Digestive Tract (propelling of food forward) SHOULD BE FORWARD 1. Smooth muscle movements with tonic/clonic movements

a. Innervation – enteric nervous system – inside the wall of GI tract b. Rhythmic movements – intermittent contraction for mixing & moving c. Peristaltic movements – contractile band forward movement * Wave movement

* Propulsive movements/Contraction starts behind substance the longitudinal shorten, circular moves chyme forward d. Segmentation – churn substances no actual directional moving 2. Innervation – enteric nervous system – inside the wall of GI tract a. Intramural neurons (myenteric & submucosal plexuses) – ANS affects stretch & chemoreceptor for chemical balance (pH, protein & fats) * Myenteric plexus – between circular & longitudinal layers * Interconnecting neurons extending entire length of GI

* Function- motility
* Submucosal (Meissner) plexus – between mucosal & circular muscles * Function- control of motility, intestinal secretions, absortion * Communicate with receptors in mucosal, muscle, mechanical & chemical responses b. Autonomic Nervous System (both parasympathetic & sympathetic) * Parasympathetic via vagus nerve to stomach, small intestine, cecum, ascending colon & transverse colon * Parasympathetic fibers via pelvic nerve

* Excitatory
* Sympathetic via thoracic chain of sympathetic ganglia, celiac, superior mesenteric & inferior mesenteric ganglia * Mediated by neurons in intramural plexuses
* Function: control mucus secretion, reduces motility by inhibiting intramural plexus, enhances sphincter tone, increases smooth muscle tone of blood vessels

II. Organs of GI Tract
A. Oral Cavity
1. Function
a. Initial entry & sensation
b. Initial dismantle through mechanical processes
c. Lubricates...
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