Study Guide: Cardiovascular, Lymphatic, Respiratory, and Digestive Systems

Cardiovascular System

Blood Vessel Types and Functions

The cardiovascular system is composed of various blood vessels that transport blood throughout the body. Each vessel type has unique structural and functional characteristics.

• Arteries: Carry blood away from the heart; have thick, strong walls to withstand high pressure.

• Arterioles: Smaller branches of arteries; lead into capillary beds.

• Capillaries: Connect arterioles to venules; primary site for nutrient, gas, and waste exchange between blood and tissues.

• Venules: Receive blood from capillaries; begin the return flow to the heart.

• Veins: Carry blood toward the heart; have thinner walls than arteries and contain valves to prevent backflow. Approximately two-thirds of blood volume is found in veins and venules at any time.

Vasoconstriction and Vasodilation

These processes regulate blood flow and pressure by altering vessel diameter.

• Vasoconstriction: Narrowing of blood vessels; decreases blood flow, increases resistance, and can raise blood pressure.

• Vasodilation: Widening of blood vessels; increases blood flow, decreases resistance, and can lower blood pressure.

Hydrostatic vs. Osmotic Pressure

These pressures control fluid movement across capillary walls.

• Hydrostatic Pressure: The force exerted by blood against vessel walls, mainly due to heart contraction; pushes fluid out of capillaries into tissues.

• Osmotic Pressure: Caused by plasma proteins in the blood; pulls fluid back into capillaries from tissues.

Together, these pressures regulate the exchange of fluids at the capillary level.

Venous Return to the Heart

• Veins contain venous valves to ensure one-way blood flow toward the heart.

• Venous pathways often parallel arteries.

• Blood from the heart muscle drains via cardiac veins into the coronary sinus and then into the heart.

Blood Pressure and Pulse Pressure

• Blood Pressure: The force blood exerts on vessel walls, typically measured in systemic arteries as systolic/diastolic pressure (mm Hg).

• Pulse Pressure: The difference between systolic and diastolic pressures.

Equation:

$\text{Pulse Pressure} = \text{Systolic Pressure} - \text{Diastolic Pressure}$

Valves in the Cardiovascular System

• Heart Valves: Located between heart chambers and at ventricular exits; include atrioventricular (AV) and semilunar valves. They prevent backflow and produce heart sounds ("Lubb" = AV valves closing; "Dupp" = semilunar valves closing).

• Vein Valves: Located inside veins; ensure one-way movement of blood toward the heart.

Oxygen-Rich vs. Oxygen-Poor Blood

• Oxygen-poor blood: Found in the right side of the heart, pulmonary arteries, and systemic veins.

• Oxygen-rich blood: Found in the left side of the heart, pulmonary veins, and systemic arteries.

This distribution is due to the pulmonary circuit (right heart → lungs → left heart) and systemic circuit (left heart → body → right heart).

Lymphatic and Immune Systems

Role in Body Fluid Balance

The lymphatic system returns excess interstitial fluid to the bloodstream, helping maintain fluid balance and working closely with the cardiovascular system.

Lymphatic Vessel Structure

• Similar to veins but with thinner walls.

• Three layers: inner endothelial lining, middle smooth muscle and elastic fibers, outer connective tissue.

• Contain semilunar valves for one-way flow.

Flow of Lymph

• Lymphatic capillaries → lymphatic vessels → lymph nodes → larger lymphatic vessels → lymphatic trunks → collecting ducts → subclavian veins.

Functions of Lymph

• Returns excess interstitial fluid and small proteins to the bloodstream.

• Absorbs dietary fats via lacteals in the small intestine.

• Transports foreign particles to lymph nodes for immune response.

• Helps defend the body against disease.

Lymph Node Structure and Function

• Contain macrophages and lymphocytes; centers for lymphocyte production.

• Filter lymph as it flows through; macrophages engulf debris and pathogens.

Spleen Structure and Function

• Part of the lymphatic system; contains lymphocytes and macrophages.

• Functions in immune surveillance and monitoring body fluids for pathogens.

Innate vs. Adaptive Defenses

• Innate (nonspecific) defenses: Present at birth; respond quickly and similarly to many pathogens.

• Adaptive (specific) defenses: Develop after exposure to antigens; specific to particular pathogens; involve B and T lymphocytes.

Antibodies: Types, Production, and Function

• Antibodies (immunoglobulins): Y-shaped proteins made of two heavy and two light chains; produced by plasma cells (activated B cells).

• Types and Relative Amounts:

Type	Relative Amount	Main Function
IgG	80%	Acts on bacteria, viruses, toxins
IgA	13%	Found in exocrine secretions
IgM	6%	Acts on food antigens, bacteria
IgD	<1%	On B-cell surfaces; common in infants
IgE	<1%	In exocrine secretions; involved in allergies

• Antigen-Antibody Relationship: Antigens are foreign substances that stimulate immune response; antibodies bind specifically to antigens, leading to direct attack, complement activation, or inflammation.

B Cell vs. T Cell Functions

• B Cells: Differentiate into plasma cells (produce antibodies) and memory B cells.

• T Cells: Participate in cell-mediated immunity, form memory T cells, and help regulate immune responses.

Cellular Immune Response

• Involves T cells responding directly to antigens; forms the basis of adaptive immunity.

• Memory T cells enable faster, stronger responses upon re-exposure to the same antigen.

Respiratory System

Ventilation and Respiratory Cycle

Ventilation (breathing) consists of inspiration (inhalation) and expiration (exhalation). One inspiration plus one expiration equals a respiratory cycle.

Structures of the Respiratory Tract

• Pharynx: Passageway for food and air; aids in sound production; divided into nasopharynx, oropharynx, and laryngopharynx.

• Larynx: Moves air in and out of trachea; houses vocal cords; contains thyroid, cricoid, and epiglottic cartilages.

• Trachea: Splits into right and left primary bronchi; lined with ciliated epithelium and supported by C-shaped cartilage rings.

• Bronchi and Bronchioles: Bronchi branch repeatedly to form the bronchial tree; bronchioles are smaller airways with smooth muscle.

• Lungs: Contain bronchial tree and alveoli; covered by visceral and parietal pleura with pleural cavity in between.

Mechanics of Inspiration

• Diaphragm and external intercostal muscles contract, enlarging the thoracic cavity.

• Lung volume increases, pressure inside lungs decreases.

• Air moves from higher atmospheric pressure into lower pressure in the lungs.

Partial Pressures of Gases

• Each gas in a mixture exerts a partial pressure proportional to its concentration.

• Changes in respiratory rate alter O2 and CO2 concentrations in body fluids.

• Chemoreceptors monitor partial pressures, CO2 levels, and blood pH.

Pleural Membranes and Pulmonary Surfactant

• Visceral pleura: Covers lung surface.

• Parietal pleura: Lines thoracic cavity.

• Pleural cavity: Contains fluid to reduce friction.

• Pulmonary surfactant: Secreted by type II alveolar cells; reduces surface tension in alveoli.

Lung Volumes and Capacities

• Tidal Volume (TV): Air moved in a normal breath.

• Inspiratory Reserve Volume (IRV): Extra air inhaled after normal inspiration.

• Expiratory Reserve Volume (ERV): Extra air exhaled after normal expiration.

• Vital Capacity (VC): Total movable air; $\text{VC} = \text{TV} + \text{IRV} + \text{ERV}$

Respiratory Effects on Blood pH

• CO2 concentration affects blood pH; increased acidity (lower pH) promotes O2 release from hemoglobin.

• Breathing rate helps regulate acid-base balance.

Hyperventilation Effects

• Alters partial pressures of O2 and CO2 in blood and body fluids.

• Changes chemoreceptor stimulation and breathing control.

Alveoli Structure and Function

• Composed mainly of simple squamous epithelium (type I cells); type II cells secrete surfactant.

• Alveolar pores connect adjacent alveoli.

• Provide large surface area for gas exchange: O2 diffuses into blood, CO2 diffuses out.

Barriers to Respiratory Infection and Dysfunction

• Mucus and cilia trap and move particles out of airways.

• Reflexes like coughing and sneezing help clear airways.

• Dysfunction (e.g., emphysema, lung cancer) damages lung tissue and impairs function.

Oxygen Transport in Blood

• O2 is transported dissolved in plasma and bound to hemoglobin (as oxyhemoglobin).

• Factors increasing O2 release from hemoglobin: increased CO2, decreased pH, increased temperature.

Digestive System

Alimentary Canal Structure

The alimentary canal is a continuous tube from mouth to anus, with four main layers:

• Mucosa

• Submucosa

• Muscularis

• Serosa

These layers facilitate digestion and movement of food.

Functions of the Digestive System

• Mechanical digestion: Physical breakdown of food (e.g., mastication).

• Chemical digestion: Enzymatic breakdown of food molecules.

• Absorption: Uptake of nutrients into the bloodstream.

• Elimination: Removal of indigestible waste.

Autonomic Regulation of Digestion

• Parasympathetic impulses: Increase digestive activity.

• Sympathetic impulses: Decrease digestive activity.

Mastication and Salivation

• Mastication: Mechanical breakdown of food in the mouth.

• Salivation: Salivary glands secrete saliva, moistening food and beginning carbohydrate digestion.

Digestive Tract Anatomy

• Esophagus: Muscular tube from pharynx to stomach; contains mucous glands and lower esophageal sphincter.

• Stomach: J-shaped pouch; mixes food with gastric juice; begins protein digestion; limited absorption.

• Small Intestine: Extends from pyloric sphincter to large intestine; completes digestion and absorbs nutrients.

• Large Intestine: Absorbs water and electrolytes; forms feces; contains intestinal bacteria.

• Liver: Four lobes; functional units are lobules with hepatocytes; produces bile and processes nutrients.

• Gallbladder: Stores and concentrates bile.

• Pancreas: Endocrine (insulin, glucagon) and exocrine (digestive enzymes) functions.

Pancreatic Enzymes

• Pancreatic amylase: Digests carbohydrates.

• Pancreatic lipase: Digests fats.

• Trypsin & chymotrypsin: Digest proteins.

• Carboxypeptidase: Digests proteins.

• Nucleases: Digest nucleic acids.

• Bicarbonate ions: Neutralize stomach acid.

Functions of the Liver and Pancreas

• Liver: Produces bile, processes nutrients, and allows blood and bile flow through lobules.

• Pancreas: Produces digestive enzymes and hormones regulating blood glucose.

Components of Bile

• Water

• Bile salts

• Bile pigments

• Cholesterol

• Electrolytes

Functions of the Small and Large Intestine

• Small Intestine: Completes digestion, absorbs nutrients, moves residue to large intestine.

• Large Intestine: Absorbs water (about 90%) and electrolytes, forms and stores feces, contains bacteria, secretes mucus.

Digestive Enzymes of Stomach and Pancreas

• Stomach: Gastric juice contains pepsin, which begins protein digestion.

• Pancreas: Secretes enzymes for all major nutrient types.

Peristalsis and Segmentation

• Peristalsis: Propelling movement that pushes food forward through the digestive tract.

• Segmentation: Mixing movement in the small intestine that aids digestion and absorption.