Chapter 20 – Lymphatic and Immune Systems

Overview of the Lymphatic and Immune Systems

The lymphatic and immune systems work together to defend the body against pathogens and maintain fluid balance. The lymphatic system transports lymph, a fluid containing infection-fighting white blood cells, throughout the body.

• Pathogen: Any microorganism or agent (such as bacteria, viruses, fungi, or parasites) that can cause disease in a host organism.

• Lymphatic Capillaries: Small, thin-walled vessels where interstitial fluid enters the lymphatic system to become lymph.

• Vascular Capillaries: Blood capillaries involved in fluid exchange with tissues.

Lymphatic System Structure

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

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

• Right Lymphatic Duct & Thoracic Duct: Major ducts that return lymph to the venous circulation.

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

Lymphatic Organs

• Primary Lymphatic Organs:

  • Bone Marrow: Site of hematopoiesis (blood cell formation), including lymphocytes.

  • Thymus: Site of T lymphocyte maturation.

• Secondary Lymphatic Organs:

  • Lymph Nodes: Filter lymph and house lymphocytes that respond to pathogens.

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

  • Tonsils: Lymphatic tissue in the pharynx that protects against inhaled or ingested pathogens.

Immunity

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

• Adaptive (Specific) Immunity: Targeted defense involving lymphocytes (B and T cells) and memory of past infections.

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

• Second Line of Defense: Internal defenses such as phagocytes, inflammation, fever, and antimicrobial proteins.

Immune System Components

• Complement System: Group of proteins that enhance immune responses.

• Interferon: Proteins released by cells in response to viruses, inhibiting viral replication.

• Inflammation: Localized tissue response to injury or infection, characterized by redness, heat, swelling, and pain.

• Chemotaxis: Movement of immune cells toward chemical signals at infection sites.

Types of Immunity

• Humoral (Antibody-mediated) Immunity: Involves B cells producing antibodies that neutralize pathogens.

• Cellular (Cell-mediated) Immunity: Involves T cells attacking infected or abnormal cells.

Cells and Molecules of Immunity

• T Cell Receptor (TCR): Molecule on T cells that recognizes antigens.

• Major Histocompatibility Complex (MHC): Proteins on cell surfaces that present antigens to T cells.

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

• Natural Killer (NK) Cells: Lymphocytes that destroy virus-infected and tumor cells.

• Cytotoxic T Cells (CD8+): Destroy infected or cancerous cells.

• Helper T Cells (CD4+): Coordinate immune responses by activating other immune cells.

• B Cells: Produce antibodies.

• Immunoglobulin (Antibody/Ig): Proteins that specifically recognize and bind antigens.

• Memory Cells: Long-lived lymphocytes that provide rapid response upon re-exposure to a pathogen.

Immune Responses and Disorders

• Secondary Immune Response: Faster and stronger response upon second exposure to an antigen.

• Graft Rejection: Immune response against transplanted tissue.

• Allergy: Hypersensitive immune response to harmless substances.

• Sensitization: Initial exposure to an allergen that primes the immune system.

• Shock: Severe allergic (anaphylactic) or infection-induced (septic) response causing systemic symptoms.

Respiratory System

Overview of the Respiratory System

The respiratory system is responsible for gas exchange, supplying oxygen to the body and removing carbon dioxide. It consists of conducting and respiratory divisions.

Anatomy of the Respiratory System

• Conducting Division: Passages that carry air to the lungs (nose, pharynx, larynx, trachea, bronchi, bronchioles).

• Respiratory Division: Structures where gas exchange occurs (respiratory bronchioles, alveoli).

• Upper Respiratory System: Nose, nasal cavity, pharynx.

• Lower Respiratory System: Larynx, trachea, bronchi, lungs.

Key Structures

• Pharynx: Muscular tube connecting nasal and oral cavities to the larynx.

• Larynx: Voice box; contains vocal cords.

• Trachea: Windpipe; conducts air to bronchi.

• Bronchi and Bronchioles: Airways branching from trachea into lungs.

• Alveoli: Tiny air sacs where gas exchange occurs.

• Respiratory Membrane: Thin barrier between alveolar air and blood for gas exchange.

Respiratory Physiology

• Ventilation: Movement of air into and out of the lungs.

• External Respiration: Exchange of gases between air in alveoli and blood.

• Pneumothorax: Air in the pleural cavity causing lung collapse.

• Surfactant: Substance reducing surface tension in alveoli, preventing collapse.

• Bronchoconstriction: Narrowing of airways, often due to asthma or allergies.

• Eupnea: Normal, quiet breathing.

• Apnea: Temporary cessation of breathing.

• Dyspnea: Difficult or labored breathing.

Respiratory Volumes and Capacities

• Tidal Volume: Amount of air inhaled or exhaled in a normal breath.

• Inspiratory Reserve Volume: Additional air that can be inhaled after a normal inhalation.

• Expiratory Reserve Volume: Additional air that can be exhaled after a normal exhalation.

• Vital Capacity: Maximum amount of air exhaled after maximum inhalation.

• Total Lung Capacity: Total volume of the lungs after maximum inhalation.

Gas Exchange and Transport

• Boyle's Law: Pressure and volume of a gas are inversely related at constant temperature. Equation:

• Partial Pressure: Pressure exerted by a single gas in a mixture.

• Oxyhemoglobin: Hemoglobin bound to oxygen.

• Hyperventilation: Increased rate and depth of breathing.

• Hypoventilation: Decreased rate and depth of breathing.

• Respiratory Center: Brainstem region controlling breathing.

• Hypercapnia: Elevated CO2 in blood.

• Asphyxia: Severe deficiency of oxygen in the body.

Digestive System

Overview of the Digestive System

The digestive system breaks down food, absorbs nutrients, and eliminates waste. It consists of the alimentary canal and accessory organs.

Anatomy of the Digestive Tract

• Digestive Tract (Alimentary Canal): Continuous tube from mouth to anus.

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

• Peritoneum: Serous membrane lining the abdominal cavity.

• Retroperitoneal: Organs located behind the peritoneum (e.g., kidneys, pancreas).

• Greater and Lesser Omentum: Folds of peritoneum supporting abdominal organs.

Oral Cavity and Swallowing

• Uvula: Soft tissue hanging from the soft palate.

• Salivary Glands: Produce saliva containing enzymes (e.g., amylase).

• Bolus: Chewed food mixed with saliva.

• Amylase: Enzyme breaking down starch (salivary and pancreatic forms).

• Lipase: Enzyme breaking down lipids.

• Deglutition: Swallowing process.

• Peristalsis: Wave-like muscle contractions moving food through the digestive tract.

Stomach and Small Intestine

• Stomach: Organ for mechanical and chemical digestion; produces gastric juice (including pepsin and hydrochloric acid).

• Intrinsic Factor: Protein necessary for vitamin B12 absorption.

• Chyme: Semi-liquid mixture of food and digestive juices.

• 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 the small intestine wall to increase absorption.

Accessory Organs

• Pancreas: Produces digestive enzymes (trypsin, chymotrypsin, carboxypeptidase, elastase) and hormones (insulin, glucagon).

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

• Gallbladder: Stores and concentrates bile.

Large Intestine and Elimination

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

• Haustra: Pouches in the colon wall.

• Diverticulosis: Formation of small pouches in the colon wall.

• Defecation: Elimination of feces.

Digestive Physiology and Disorders

• Gastric Motility: Movement of the stomach and intestines.

• Gastrocolic Reflex: Increased colon motility after eating.

• Diarrhea and Constipation: Disorders of bowel movement frequency and consistency.

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

• Helicobacter pylori: Bacteria associated with peptic ulcers.

Nutrient Absorption and Metabolism

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

• Beta-oxidation: Metabolic process breaking down fatty acids for energy.

• Ketone Bodies: Produced during fat metabolism.

• Essential Fatty Acids and Amino Acids: Nutrients that must be obtained from the diet.

Example Table: Types of Lipoproteins

Additional info: Some terms and explanations were expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.