Patho2_Chapter35_Student.pptx

Gastrointestinal Function Chapter 35  Gastrointestinal System Functions – Provide nutrients for the body with propulsive and mixing movements – Secretion of digestive juices – Absorption of nutrients  CONGENITAL ANOMALIES – Begins to form as early as 4th week of ge...

Gastrointestinal Function Chapter 35  Gastrointestinal System Functions – Provide nutrients for the body with propulsive and mixing movements – Secretion of digestive juices – Absorption of nutrients  CONGENITAL ANOMALIES – Begins to form as early as 4th week of gestation – Atresia/Fistula/Stenosis MOST COMMON Atresia Fistula Esophageal Tracheoesophegeal Atresia plus Fistula Atresia Fistula Functional Anatomy of the GI Tract  Mouth and Salivary Glands Point of entry for nutrients Food broken down and moistened by saliva  Geriatric Considerations Atrophy of Decreased Increase Decrease bone tissue acinar cells in saliva d number salivary alkalinity of taste glands buds Loss of teeth Decrea sed Halitosis saliva Cosmetic effects Decreas ed taste  The Esophagus Straight collapsible tube about 25 cm long Peristaltic waves move food though the esophagus Mucous glands are scattered throughout the submucosa Lower esophageal sphincter (LES)  voluntary stage pharyngeal stage Breathing temporarily interrupted peristalsis Swallowing esophageal stage  Parts of the Stomach Cardiac region Small area near esophageal opening Fundus Temporary food storage area Might fill with swallowed air sometimes Antrum No rugae Pyloric region Invaginations of the stomach Gastric Pits leads to gastric glands  Needed for Vitamin B12 absorption. Sectional View of the Gastric Glands in the Stomach Mucosa  Small Intestines Small intestine – Is approximately 5-6 meters long – Duodenum First 22 cm – Jejunum Next 2 meters – Ileum Forms the remainder  Large Intestines 1.5 meters long muscular tube that forms a frame around the small intestine Large intestine – Transverse colon – Descending colon – Sigmoid colon – Rectum  GI MOTILITY CHARACTERISTICS Intestinal wall – Skeletal muscle upper end and lower end of GI tract – Muscular movements performed by close layers of smooth muscle – Neural control by CNS through the ANS – Modulated by numerous hormonal interactions Neuronal Control: Enteric Nervous System Intestinal wall controlled by INTRINSIC NERVOUS SYSTEM PNS INCREASES activity - Vagus nerve SNS DECREASES activity - Sacral segments Parasympathic vs. Sympathetic  Basic Anatomy of ANS Preganglionic neuron – cell body in brain or spinal cord – axon is myelinated fiber that extends to autonomic ganglion Postganglionic neuron – cell body lies outside the CNS in an autonomic ganglion – axon is unmyelinated fiber that terminates in a visceral effector ENHANCEMENT INHIBITION  Electrical activity of gastrointestinal smooth muscle Slow wave – Continuously present Spikes – Ach: depolarization – NE: hyperpolarizatio n  Hormonal Control Impulses operating through VAGUS NERVE stimulate gastric secretions when taste, see, smell or think about food Gastrin – Secreted by G cells  Hormonal Control Cholecystokinin Secreted by I cells of jejunum Secretin Mucosa of duodenum Gastric inhibitory peptide Secreted by mucosa of upper portion of SI in response to the presence of fat; decreases stomach motility  Intestinal Contraction of Smooth Muscle Muscular activity involved with digestion and absorption – Mixing Keeps the intestinal contents mixed on a constant basis by either peristalsis or constrictive contraction of small segments of the gut wall – Propulsive (peristalsis) Progressive movement Slow, progressive movement of a circular constriction that squeezes materials forward  Movement of Nutrients Chewing – CN V – CNVII – CNIX – CNX – CNXI – CNXII  Oral stage Pharyngeal stage Breathing temporarily interrupted peristalsis Swallowing Esophageal stage  Neuronal Control of Swallowing Swallowing receptors Trigeminal nerve Medulla oblongata Smooth/Skeletal muscles contract CN XI and CN XII CN X Oral + Esophageal Pharyngeal Stage Stage  Motility of Stomach and Small Intestines Gastric filling and storage Chyme – Milky white sludge of gastric juices and food Gastric emptying Propulsion through small intestines Mixing  Segmentation Small intestine – Segmental contractions (mixing) “Chops” chyme and mixes with digestive juices As one set of contractions is completed, a new set begins Emptying of the Ileocecal Valve Muscular coat thicker in region High pressure area Usually closed  Large intestine (colon) – Main function is fluid and electrolyte absorption – Storage of fecal mass until expelled from body – Haustral churning – Defecation Takes about 18 hours to reach distal end  Gastrointestinal Hormones Hormone Source Target Major Stimulated Organ Actions By Gastrin Stomach Gastric glands Secretin Duodenum Pancreas Cholecystoki Liver, nin Pancreas, Gall bladder Glucose- Duodenum Stomach dependent insulinotropi c Polypeptide (GIP) Regulation of Acid Secretion from Parietal Cells ECL cells H2 receptor  HCl Secretion by Gastric Parietal Cells Blood Parietal Cells Lumen of stomach The Production and Action of Pepsin Digestion and Absorption Smaller substances need to transfer across the wall into blood and lymph  Digestion Carbs – Mouth, stomach, small intestines (brush border) – Salivary/pancreatic amylase Fats – Occur in small intestines – Emulsification Bile salts break up large fat globs into droplet (emulsification) Lipase Proteins – Pepsin Breaks down proteins – Pancreatic proteases – Brush border  Absorption of H2O and Electrolytes Absorbed mainly in the Small Intestines Absorption of H2O – Water follows salt – Occurs passively by osmosis – 800 ml/day absorbed in small intestine – 300-400 ml/day absorbed in large intestine  water & ions too To the lymph Enter blood at L. subclavian v. Absorption of Digested Nutrients in the Small Intestine Absorption of Digested Nutrients in the Small Intestine Summary of Digestive Function  Aging Effects on GI System Decreased parietal and chief cells – Leads to decreased HCl and pepsin in stomach causing an increased pH (alkalinity) Epithelial membrane changes – Decreased absorption of lipids, amino acids, glucose, Ca, and Fe Decreased smooth muscle and strength – Decreased emptying time – Decreased anal sphincter tone – Increased nonperistaltic waves and decreased peristalsis  HIATAL HERNIA In ALL cases, STOMACH above diaphragm Usually associated with reflux