anaphy-111-finals-transes

Week 13: The Digestive System and Body Metabolism

  • The digestive system functions as a nutrient delivery system, similar to a large-scale "meals on wheels," providing necessary nutrients for over 100 trillion cells.

  • It also has mechanisms for quality control and waste disposal.

Digestive Processes

  • Ingestion: Placing food into the mouth.

  • Propulsion: Movement of food through the digestive tract. Includes:

    • Peristalsis: Waves of contraction and relaxation that push food along.

    • Segmentation: Back-and-forth movement promoting mixing in the small intestine.

  • Food Breakdown: Initiated by digestive enzymes like salivary amylase.

  • Absorption: The process of nutrients entering the bloodstream.

  • Defecation: Expulsion of indigestible waste from the body.

  • The alimentary canal is approximately 25 feet long and operates as a continuous, coiled tube through various organs:

    • Mouth

    • Pharynx

    • Esophagus

    • Stomach

    • Small intestine

    • Large intestine

    • Anus

Organs Related to Digestion

  • Accessory Organs: Help in digestion but are not part of the digestive tube itself. Include:

    • Mouth: Teeth, tongue, salivary glands.

    • Small Intestine: Liver, gallbladder, pancreas.

Layers of the Alimentary Canal

  1. Mucosa:

    • Innermost moist membrane consisting of:

      • Surface epithelium, primarily simple columnar (stratified squamous in esophagus).

      • Lamina propria (connective tissue).

      • Smooth muscle layer.

    • Lines the lumen (internal cavity).

  2. Submucosa:

    • Soft connective tissue with:

      • Blood vessels

      • Nerve endings

      • Mucosa-associated lymphoid tissue

      • Lymphatic vessels.

  3. Muscularis Externa:

    • Composed of smooth muscle layers:

      • Inner circular layer.

      • Outer longitudinal layer.

  4. Serosa:

    • Outermost layer containing fluid-producing cells:

      • Visceral peritoneum

      • Parietal peritoneum, lining the abdominal cavity.

Mouth: Buccal Cavity or Oral Cavity Functions

  • Mastication (chewing food).

  • Mixing food with saliva using the tongue.

  • Initiation of Swallowing:

    • Taste perception via taste buds on the tongue.

Divisions of the Mouth

  • Vestibule: Space between the lips and teeth.

  • Oral Cavity Proper: Area enclosed by the teeth.

Mouth Structures

  • Hard Palate: Anterior roof of the mouth.

  • Soft Palate: Posterior roof, muscular.

  • Uvula: Fleshy projection that helps prevent food from entering the nasal cavity during swallowing.

  • Lips (Labia): Protect the anterior opening of the mouth.

Teeth and Tongue

  • Teeth: Structure for mastication.

    • Two sets in a lifetime:

      • Deciduous Teeth: 20 temporary teeth.

      • Permanent Teeth: 32 total, including incisors, canines, premolars, and molars.

  • Tongue: Muscular structure for taste and speech:

    • Contains different types of papillae for taste sensing:

      • Filiform (no taste buds; texture enhancement)

      • Fungiform (contains taste buds)

      • Circumvallate (large, V-shaped, contains numerous buds).

  • Salivary Glands: Produce saliva to moisten food, aiding digestion:

    • Parotid Glands (largest), Submandibular Glands, Sublingual Glands (smallest).

Pharynx and Esophagus

  • Pharynx: Passageway for food and air.

    • Divided into three regions: Nasopharynx, Oropharynx, Laryngopharynx.

    • Propulsion of food via peristalsis to esophagus.

  • Esophagus: Musculo-membranous tube for food transport only (no digestion).

Swallowing Mechanism

  • Oral Phase: Voluntary, from oral cavity to oropharynx.

  • Pharyngeal Phase: Involuntary, from oropharynx to esophagus.

  • Esophageal Phase: Involuntary, moving food into stomach.

Stomach Structure and Function

  • Regions: Cardia, Fundus, Body, Pylorus (connected to small intestine).

  • Mucosa: Composed of simple columnar epithelial cells.

    • Gastric pits lead to gastric glands secreting:

      • Intrinsic factor (vitamin B12 absorption)

      • Digestive enzymes (pepsinogen, active form pepsin).

Small Intestine: Nutrient Absorption

  • Parts: Duodenum (shortest), Jejunum, Ileum (longest).

  • Villi and Microvilli: Increase absorption surface area.

  • Digestive Enzymes: Bile duct enzymes from pancreas, bile from liver.

Large Intestine Functions

  • Absorbs water and electrolytes.

  • Serves as reservoir for waste material (5 ft long).

  • Consists of:

    • Cecum (with appendix)

    • Colon (ascending, transverse, descending, sigmoid)

    • Rectum

    • Anal canal.

Accessory Digestive Organs

Pancreas

  • Retroperitoneal gland secreting digestive enzymes.

  • Functions: Produces pancreatic juice containing enzymes (lipase, amylase).

Liver

  • Largest gland; involved in metabolism, bile production, detoxification, and nutrient storage.

Gallbladder

  • Stores bile produced by the liver, assisting in fat digestion.

Week 14: The Urinary System

  • Responsible for waste elimination and homeostasis.

  • Functions include:

    • Excretion of wastes (nitrogenous, toxins, excess ions).

    • Regulation of blood pressure, red blood cell production, vitamin D activation.

Kidneys Structure

  • Located against the dorsal body wall (retroperitoneal).

  • Structure includes:

    • Renal cortex, medulla, and hilum where vessels enter.

    • Renal pyramids and pelvis for urine collection.

Urine Formation

  1. Glomerular Filtration: Blood plasma filtration.

  2. Tubular Reabsorption: Absorption of useful substances back into blood.

  3. Tubular Secretion: Selectively adding substances to urine.

Endocrine System Overview

  • Composed of ductless glands that secrete hormones, which are chemical messengers affecting distant target organs.

  • Major organs of the endocrine system regulate various functions, such as metabolism, growth, and reproduction.