Digestive_System_Detailed.pptx stu dents

Digestive System
• Anatomy, Physiology & Clinical Aspects

Learning Objectives
• Understand the structure and function of the digestive system
• Describe the process of digestion and absorption
• Identify the role of accessory organs
• Recognize common disorders of the digestive tract

Overview
• Two main groups of organs:
a)Alimentary canal (GI tract): continuous tube from mouth to anus
b)Accessory organs: aid digestion but food doesn’t pass through them
• Average length of GI tract: ~9 meters in adults
• Digestive system works via mechanical & chemical processes

Anatomy of Alimentary Canal
• Mucosa – epithelial lining, secretes mucus and enzymes
• Submucosa – connective tissue, blood vessels, nerves
• Muscularis externa – smooth muscle for peristalsis
• Serosa – outer protective layer

Mouth & Salivary Glands
• Structures: lips, cheeks, palate, tongue
• Teeth types: incisors, canines, premolars, molars
• Saliva: water, salivary amylase, mucus, lysozyme
• Function: lubrication, starch digestion begins

Pharynx
• Divisions: nasopharynx, oropharynx, laryngopharynx
• Role: passage for food and air
• Swallowing stages: voluntary, pharyngeal, esophageal

Esophagus
• Length ~25 cm
• Peristalsis: rhythmic muscular contractions pushing food to stomach
• Lower esophageal sphincter prevents acid reflux

Stomach
• Regions: cardia, fundus, body, pylorus
• Gastric juice: HCl, pepsinogen → pepsin
• Mucus protects lining from acid
• Mechanical churning forms chyme
• Food stays ~4 hours

Small Intestine
• Sections: duodenum, jejunum, ileum
• Enzymes from pancreas & bile from liver aid digestion
• Villi & microvilli increase surface area for absorption

Large Intestine
• Parts: cecum, appendix, colon, rectum, anus
• Functions: water absorption, vitamin synthesis, feces formation
• Gut flora produce vitamins

Liver
• Largest gland in body (~1.5 kg)
• Produces bile for fat emulsification
• Stores glycogen, processes nutrients, detoxifies drugs/toxins
• Makes plasma proteins

Gallbladder
• Stores & concentrates bile
• Releases bile into duodenum
• Disorders: gallstones

Pancreas
• Exocrine: produces digestive enzymes & bicarbonate
• Endocrine: secretes insulin & glucagon

Digestive Enzymes
• Amylase – starch digestion
• Pepsin – protein digestion
• Lipase – fat digestion
• Lactase – milk sugar digestion

Process of Digestion
• Ingestion
• Propulsion – swallowing, peristalsis
• Mechanical digestion – chewing, churning
• Chemical digestion – enzymes, acid, bile
• Absorption – nutrients into blood & lymph
• Defecation – elimination of waste

Absorption Mechanisms
• Passive diffusion
• Facilitated diffusion
• Active transport
• Endocytosis

Regulation of Digestion
• Nervous: enteric nervous system, vagus nerve
• Hormonal: gastrin, secretin, CCK, GIP

Common Disorders
• GERD – acid reflux
• Ulcers – H. pylori infection
• Irritable bowel syndrome (IBS)
• Gallstones
• Hepatitis

Nutrition & Digestive Health
• Balanced diet with fiber, adequate hydration
• Avoid excessive fatty/spicy foods
• Probiotics for gut health

Summary
• Digestive system = coordinated organs & enzymes
• Converts food into energy & building blocks
• Maintains health & homeostasis

Digestive_System_Detailed.pptx stu dents

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