Anatomy & Physiology Study Notes: Lymphatic, Immune, Respiratory, and Digestive Systems

Chapter 20 – Lymphatic and Immune System

Overview of the Lymphatic System

The lymphatic system is a network of vessels and organs that helps maintain fluid balance, absorbs fats, and plays a crucial role in immune defense.

• Lymphatic capillaries: Small, thin-walled vessels where interstitial fluid enters the lymphatic system.

• Vascular capillaries: Blood capillaries involved in fluid exchange (review for comparison).

• Lacteal: Specialized lymphatic capillaries in the small intestine that absorb dietary fats.

• Lymphatic trunk: Large lymphatic vessels that drain lymph from regions of the body.

• Thoracic duct: Main lymphatic vessel returning lymph to the bloodstream.

• Edema: Swelling caused by excess fluid in tissues, often due to lymphatic obstruction.

Lymphatic Organs

• Primary lymphatic organs: Sites of lymphocyte production and maturation.

  • Bone marrow: Produces B and T lymphocytes; B cells mature here.

  • Thymus: T cells mature here.

• Secondary lymphatic organs: Sites where immune responses are initiated.

  • Lymph nodes: Filter lymph and house immune cells.

  • Spleen: Filters blood, removes old red blood cells, and mounts immune responses.

  • Tonsils: Protect against pathogens entering through the mouth and nose.

Immune System Overview

The immune system defends against pathogens—any microorganism or agent that can cause disease in a host organism.

• Innate (Non-specific) Immunity: Immediate, general defense mechanisms (e.g., skin, mucous membranes, phagocytes).

• Adaptive (Specific) Immunity: Targeted responses involving lymphocytes and memory cells.

• First Line of Defense: Physical and chemical barriers (skin, mucous membranes).

• Second Line of Defense: Internal defenses (complement system, interferon, inflammation, chemotaxis).

• Humoral Immunity: Antibody-mediated, involving B cells and immunoglobulins.

• Cellular Immunity: Cell-mediated, involving T cells (cytotoxic CD8+, helper CD4+).

Key Immune Components

• T cell receptor (TCR): Recognizes antigens presented by APCs.

• Major Histocompatibility Complex (MHC): Proteins presenting antigens to T cells.

• Antigen-presenting cell (APC): Cells (e.g., dendritic cells, macrophages) that display antigens.

• Natural Killer cells: Destroy infected or abnormal cells.

• B cell: Produces antibodies (immunoglobulins).

• Memory cells: Provide long-term immunity.

Immune Responses and Disorders

• Secondary immune response: Faster, stronger response upon re-exposure to antigen.

• Graft rejection: Immune response against transplanted tissue.

• Allergy: Hypersensitive immune response to harmless antigens.

• Sensitization: Initial exposure leading to heightened response.

• Shock: Severe allergic (anaphylactic) or septic response.

Respiratory System

Overview and Divisions

The respiratory system enables gas exchange, supplying oxygen and removing carbon dioxide. It is divided into conducting and respiratory divisions.

• Conducting division: Passages that transport air (nose, pharynx, larynx, trachea, bronchi).

• Respiratory division: Sites of gas exchange (alveoli).

• Upper respiratory system: Nose, nasal cavity, pharynx.

• Lower respiratory system: Larynx, trachea, bronchi, lungs.

Key Structures and Functions

• Pharynx: Passageway for air and food; includes nasopharynx, oropharynx, laryngopharynx.

• Larynx: Voice box; contains thyroid and cricoid cartilage, epiglottis, glottis.

• Trachea: Windpipe; supported by cartilage rings.

• Bronchi: Right and left main bronchi branch into bronchioles.

• Alveoli: Tiny air sacs for gas exchange.

• Respiratory membrane: Barrier for gas exchange between alveoli and capillaries.

• Ventilation: Movement of air in and out of lungs.

• External respiration: Exchange of gases between lungs and blood.

Respiratory Physiology

• Pneumothorax: Air in pleural cavity causing lung collapse.

• Surfactant: Substance reducing surface tension in alveoli.

• Bronchoconstriction: Narrowing of airways.

• Eupnea: Normal breathing.

• Apnea: Absence of breathing.

• Dyspnea: Difficulty breathing.

Respiratory Volumes and Gas Laws

• Tidal volume: Air moved per breath.

• Inspiratory reserve volume: Extra air inhaled after normal inspiration.

• Expiratory reserve volume: Extra air exhaled after normal expiration.

• Vital capacity: Maximum air exhaled after maximum inhalation.

• Total lung capacity: Total volume in lungs after maximum inhalation.

• Boyle's Law: Pressure and volume of a gas are inversely related. Equation: $P_1V_1 = P_2V_2$

• Partial pressure: Pressure exerted by each gas in a mixture.

• Oxyhemoglobin: Hemoglobin bound to oxygen.

• Hyperventilation: Increased rate/depth of breathing.

• Hypoventilation: Decreased rate/depth of breathing.

• Respiratory center: Brain region controlling breathing.

• Hypercapnia: Elevated CO2 in blood.

• Asphyxia: Oxygen deprivation.

Digestive System

Digestive Tract and Processes

The digestive system breaks down food, absorbs nutrients, and eliminates waste. The alimentary canal is the main passage for food.

• Digestion: Mechanical and chemical breakdown of food.

• Secretion: Release of digestive enzymes and fluids.

• Absorption: Uptake of nutrients into blood or lymph.

• Defecation: Elimination of undigested material.

Histology and Anatomy

• Mucosa, Submucosa, Muscularis, Serosa: Layers of the digestive tract wall.

• Peritoneum: Serous membrane lining abdominal cavity.

• Retroperitoneal: Organs located behind the peritoneum.

• Greater omentum: Fatty apron over intestines.

• Salivary glands: Produce saliva for digestion.

• Uvula: Prevents food from entering nasopharynx.

• Bolus: Chewed food ready to swallow.

Digestive Enzymes and Processes

• Amylase: Breaks down starch (salivary and pancreatic).

• Lipase: Breaks down fats.

• Peristalsis: Wave-like muscle contractions moving food.

• Deglutition: Swallowing.

• Esophageal hiatus: Opening in diaphragm for esophagus.

Stomach and Pancreas

• Stomach: Secretes gastric juice, intrinsic factor, pepsinogen, and pepsin for protein digestion.

• Pancreas: Produces digestive enzymes (trypsin, chymotrypsin, carboxypeptidase, elastase).

Liver and Gallbladder

• Liver: Produces bile, processes nutrients, detoxifies substances.

• Gallbladder: Stores and concentrates bile.

• Common hepatic ducts: Transport bile from liver.

• Hepatitis: Inflammation of the liver.

• Cirrhosis: Chronic liver damage.

Small and Large Intestine

• Small intestine: Main site of nutrient absorption; includes duodenum, jejunum, ileum.

• Villi and microvilli: Increase surface area for absorption.

• Circular folds (plicae circulares): Folds in small intestine wall.

• Chylomicron: Lipoprotein transporting dietary fats.

• Large intestine: Absorbs water, forms feces; includes cecum, colon, rectum.

• Haustra: Pouches in colon wall.

• Diverticulosis: Formation of pouches in colon wall.

Digestive Reflexes and Disorders

• Gastrocolic reflex: Increased colon motility after eating.

• Defecation reflex: Initiates elimination.

• Diarrhea, constipation: Disorders of bowel movement.

• Cholecystokinin (CCK): Hormone stimulating bile and pancreatic enzyme release.

• Helicobacter pylori: Bacteria causing ulcers.

Nutrient Metabolism

• Lipoproteins: Transport lipids in blood (HDL, LDL, VLDL).

• Beta-oxidation: Fatty acid breakdown for energy.

• Ketone bodies: Produced during fat metabolism.

• Essential fatty acids and amino acids: Must be obtained from diet.

• Gluconeogenesis: Formation of glucose from non-carbohydrate sources.

• Lipogenesis: Formation of fat from excess nutrients.