BIOH 211: Comprehensive Study Guide for Blood, Heart, Circulatory, Lymphatic, Immune, Respiratory, Endocrine, Digestive, Metabolic, Urinary, Fluid/Electrolyte, and Reproductive Systems

Blood

General Functions and Composition of Blood

The blood is a vital connective tissue responsible for transport, regulation, and protection within the body.

• Major Functions: Transport of gases, nutrients, hormones, and waste; regulation of pH, temperature, and fluid volume; protection against blood loss and infection.

• General Composition: Blood consists of plasma (liquid matrix) and formed elements (cells and cell fragments).

• Plasma Components: Water, plasma proteins (albumins, globulins, fibrinogen), electrolytes, nutrients, gases, and waste products.

• Plasma Proteins: Albumin (osmotic pressure, transport), globulins (immunity, transport), fibrinogen (clotting); produced mainly by the liver.

• Leukocytes: Five types in order of prevalence: neutrophils, lymphocytes, monocytes, eosinophils, basophils. Each has distinct immune functions.

• Formed Elements: Erythrocytes (RBCs), leukocytes (WBCs), and platelets (thrombocytes).

• Hematocrit: The percentage of blood volume occupied by erythrocytes. Calculated as: $\text{Hematocrit} = \frac{\text{Volume of RBCs}}{\text{Total Blood Volume}} \times 100$

• Factors Affecting Hematocrit: Dehydration, blood loss, anemia, polycythemia.

Hematopoiesis

Hematopoiesis is the process of blood cell formation, primarily occurring in the red bone marrow.

• Erythropoiesis: Production of erythrocytes; regulated by erythropoietin (EPO) from the kidneys. Reticulocytes are immature RBCs.

• Hemoglobin: Oxygen-carrying protein in RBCs; composed of globin chains and heme groups. Breakdown products include bilirubin and iron.

• Anemia: Reduced oxygen-carrying capacity; categories include inadequate production, hemolytic, and hemorrhagic anemia.

• Leukopoiesis: Formation of WBCs; regulated by colony-stimulating factors.

• Thrombopoiesis: Formation of platelets from megakaryocytes; regulated by thrombopoietin.

Hemostasis

Hemostasis is the process that stops bleeding following vascular injury.

• Phases: Vascular spasm, platelet plug formation, coagulation.

• Vascular Spasm: Vasoconstriction mediated by endothelial cells and serotonin.

• Platelet Plug: Platelets adhere to exposed collagen, aggregate, and release chemicals.

• Coagulation: Intrinsic and extrinsic pathways converge at factor X, leading to fibrin clot formation.

• Fibrinolysis: Breakdown of clots via plasminogen, tPA, and plasmin.

• Aspirin: Inhibits platelet aggregation, reducing unwanted clot formation.

ABO and Rh Blood Typing

Blood typing is essential for safe transfusions and understanding immune reactions.

• ABO Types: Determined by surface antigens (A, B) and plasma antibodies.

• Rh Factor: Presence (+) or absence (−) of D antigen.

• Agglutination: Clumping of RBCs due to antibody-antigen reaction.

• Transfusion Compatibility: Based on matching antigens and avoiding antibody reactions.

• Anti-Rh Antibodies: Develop after exposure; Rhogam prevents sensitization in Rh− mothers.

The Heart

Microscopic and Gross Anatomy

The heart is a muscular organ located in the thoracic cavity, responsible for pumping blood through the circulatory system.

• Position: Mediastinum, between lungs, apex points left.

• Pericardium: Fibrous and serous layers; serous fluid reduces friction.

• Heart Chambers: Two atria (receiving), two ventricles (pumping).

• Heart Wall Layers: Epicardium (outer), myocardium (muscular), endocardium (inner).

• Myocardium: Contains intercalated discs for electrical connectivity.

• Coronary Circulation: Supplies heart muscle; includes right/left coronary arteries, coronary sinus.

Blood Flow Through the Heart

Blood flows through the heart in a specific sequence, passing through valves to prevent backflow.

• Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery → lungs → pulmonary veins → left atrium → bicuspid (mitral) valve → left ventricle → aortic valve → aorta.

Physiology of Cardiac Muscle Contraction

Cardiac muscle contraction is initiated by pacemaker cells and propagated through the myocardium.

• Pacemaker Cells: Generate spontaneous action potentials via ion channel activity (Na+, Ca2+, K+).

• Contractile Cells: Respond to action potentials with Ca2+-mediated contraction.

• Autonomic Regulation: Sympathetic increases rate/force; parasympathetic decreases rate.

Cardiac Cycle

The cardiac cycle describes the sequence of events in one heartbeat.

• Phases: Ventricular filling, isovolumetric contraction, ventricular ejection, isovolumetric relaxation.

• Systole: Contraction phase; Diastole: Relaxation phase.

• Heart Sounds: First (S1) and second (S2) sounds correspond to valve closures.

Regulation of Cardiac Output, Stroke Volume, and Heart Rate

Cardiac output (CO) is the volume of blood pumped per minute.

• CO Formula: $\text{CO} = \text{HR} \times \text{SV}$

• Stroke Volume (SV): $\text{SV} = \text{EDV} - \text{ESV}$

• Ejection Fraction: $\text{EF} = \frac{\text{SV}}{\text{EDV}} \times 100$

• Venous Return, Preload, Afterload: Affect SV and CO.

• Frank-Starling Law: Increased preload increases SV.

• Inotropic Agents: Affect contractility; Chronotropic Agents: Affect HR.

Electrical Conduction System and ECG

The heart's electrical system coordinates contraction and is measured by the electrocardiogram (ECG).

• Conduction Pathway: SA node → AV node → Bundle of His → bundle branches → Purkinje fibers.

• ECG Deflections: P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization).

• Arrhythmias: Abnormal rhythms; ectopic focus: Abnormal pacemaker site.

The Circulatory System

Blood Vessels

Blood vessels transport blood throughout the body and are classified by structure and function.

• Arteries: Carry blood away from the heart.

• Veins: Return blood to the heart.

• Capillaries: Sites of exchange between blood and tissues.

• Three Tunics: Tunica intima (endothelium), tunica media (smooth muscle), tunica externa (connective tissue).

• Vasoconstriction/Vasodilation: Narrowing/widening of vessels.

• Capillary Types: Continuous, fenestrated, sinusoidal; structure relates to function.

• Anastomosis: Connection between vessels; provides alternate pathways (e.g., Circle of Willis).

Systemic and Pulmonary Circuits

The circulatory system is divided into systemic (body) and pulmonary (lungs) circuits.

• Systemic Circuit: Delivers oxygenated blood to tissues.

• Pulmonary Circuit: Carries deoxygenated blood to lungs for gas exchange.

• Portal System: Blood passes through two capillary beds (e.g., hepatic portal system).

Fetal vs. Postnatal Circulation

Fetal circulation includes unique structures that change after birth.

• Fetal Structures: Foramen ovale, ductus arteriosus, ductus venosus.

• Postnatal Remnants: Fossa ovalis, ligamentum arteriosum, ligamentum venosum.

Blood Pressure and Hemodynamics

Blood pressure is the force exerted by blood on vessel walls and is regulated by cardiac output and resistance.

• Blood Pressure (BP): $\text{BP} = \text{CO} \times \text{TPR}$

• Pulse Pressure (PP): $\text{PP} = \text{Systolic BP} - \text{Diastolic BP}$

• Mean Arterial Pressure (MAP): $\text{MAP} = \text{Diastolic BP} + \frac{1}{3}(\text{Systolic BP} - \text{Diastolic BP})$

• Capillary Exchange: Driven by hydrostatic and osmotic pressures.

• Edema: Results from imbalance in filtration/reabsorption or lymphatic dysfunction.

• Hormonal Regulation: ADH, angiotensin II, aldosterone, ANP, epinephrine, norepinephrine.

• Baroreceptor Reflex: Maintains BP homeostasis via neural feedback.

Circulatory Shock

Shock is a life-threatening condition of inadequate tissue perfusion.

• Types: Hypovolemic (blood loss), vascular (vasodilation), cardiogenic (heart failure).

• Compensatory Mechanisms: Increased HR, vasoconstriction, fluid retention.

• EpiPen: Delivers epinephrine to reverse anaphylactic shock.

Lymphatic and Immune Systems

Lymphatic System Structure and Function

The lymphatic system returns interstitial fluid to the bloodstream and participates in immune defense.

• Structures: Lymphatic vessels, lymph nodes, spleen, thymus, tonsils.

• Lymph Formation: Derived from interstitial fluid; circulates through lymphatic vessels to veins.

• Lymph Flow: Right leg → lymphatic capillaries → vessels → nodes → thoracic duct → left subclavian vein.

Immune Defense Mechanisms

The immune system provides three lines of defense against pathogens.

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

• Second Line: Innate immunity (phagocytes, inflammation, fever, complement, interferons).

• Third Line: Adaptive immunity (B and T lymphocytes, antibodies).

• Key Terms: Diapedesis (WBC movement), chemotaxis (chemical attraction), opsonization (enhanced phagocytosis).

• Phagocytosis: Engulfment and destruction of pathogens by neutrophils, macrophages.

• Inflammation: Redness, heat, swelling, pain; benefits include containment and repair.

• Fever: Elevated body temperature; pyrogens reset hypothalamic set point.

Adaptive Immunity

Adaptive immunity involves specific recognition and memory of pathogens.

• Antigen-Presenting Cells (APCs): Dendritic cells, macrophages, B cells.

• Cell Types: NK cells, dendritic cells, B cells, plasma cells, helper T cells, cytotoxic T cells, memory cells.

• Epitope: Specific region of antigen recognized by immune cells.

• Antibody Classes: IgG, IgA, IgM, IgE, IgD; each with unique locations and functions.

• Primary vs. Secondary Response: Secondary is faster, stronger, mainly IgG.

• Cell-Mediated Immunity: Cytotoxic T cells destroy infected cells using perforin and granzymes.

• Active vs. Passive Immunity: Active (infection/vaccination), passive (antibodies from another source).

• Hypersensitivity: Type I (acute, allergy), Type IV (delayed, contact dermatitis).

Respiratory System

Structure and Function

The respiratory system enables gas exchange between the body and environment.

• Structures: Nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli.

• Histology: Varies by region; alveoli have thin walls for gas exchange.

• Airflow Pathway: Nares → pharynx → larynx → trachea → bronchi → bronchioles → alveolar sacs.

Mechanics of Breathing

Ventilation is driven by pressure differences created by respiratory muscles.

• Pressures: Atmospheric, intrapulmonary, intrapleural, transpulmonary.

• Boyle's Law: $P_1V_1 = P_2V_2$; pressure inversely related to volume.

• Muscles: Diaphragm, external intercostals (inspiration); internal intercostals, abdominal muscles (expiration).

• Dead Space: Air not involved in gas exchange.

• Alveolar Membrane: Three layers: alveolar epithelium, basement membrane, capillary endothelium.

• Surfactant: Reduces surface tension, prevents alveolar collapse.

Gas Exchange and Transport

Oxygen and carbon dioxide are exchanged and transported by specific mechanisms.

• External (Alveolar) Exchange: O2 into blood, CO2 out.

• Internal (Systemic) Exchange: O2 to tissues, CO2 to blood.

• Oxygen Transport: Mostly bound to hemoglobin.

• CO2 Transport: Dissolved, bound to hemoglobin, as bicarbonate (majority).

• CO2 Reaction: $\mathrm{CO_2 + H_2O \leftrightarrow H_2CO_3 \leftrightarrow H^+ + HCO_3^-}$

• Chloride Shift: Exchange of Cl− and HCO3− in RBCs.

• Oxygen-Hemoglobin Curve: Right shift (↓affinity) with ↑temperature or ↓pH; left shift (↑affinity) with ↓temperature or ↑pH.

Control of Respiration

• Respiratory Centers: Medulla (ventral and dorsal groups), pons.

• Stimuli: CO2, O2, pH, neural input.

• Eupnea: Normal quiet breathing controlled by ventral respiratory group.

Endocrine System

Overview and Hormone Action

The endocrine system regulates body functions via hormones secreted into the bloodstream.

• Nervous vs. Endocrine: Nervous is fast, short-term; endocrine is slower, long-term.

• Hormone Classes: Amino acid-based (e.g., insulin), steroids (e.g., cortisol).

• Transport and Receptors: Steroids are lipid-soluble, act on intracellular receptors; amino acid-based are water-soluble, act on membrane receptors.

• Second Messengers: cAMP, DAG, IP3; hormones activate specific pathways.

• Hormone Interactions: Permissiveness, synergism, antagonism.

Major Endocrine Organs and Hormones

• Hypothalamus: Regulates pituitary via releasing/inhibiting hormones.

• Pituitary Gland: Anterior (GH, TSH, ACTH, etc.), posterior (ADH, oxytocin).

• Thyroid: Thyroxine (T4), triiodothyronine (T3), calcitonin.

• Adrenal Gland: Cortex (cortisol, aldosterone), medulla (epinephrine, norepinephrine).

• Pancreas: Insulin, glucagon.

• Parathyroid: Parathyroid hormone (PTH).

• Thymus: Thymosins.

Hormonal Disorders

• Examples: Grave’s disease, Hashimoto’s, diabetes mellitus (type I/II), diabetes insipidus, Cushing’s, Addison’s, gigantism, acromegaly, pituitary dwarfism.

Digestive System

Structure and Function

The digestive system breaks down food, absorbs nutrients, and eliminates waste.

• Layers: Mucosa, submucosa, muscularis externa, serosa/adventitia.

• Mesenteries: Support and anchor digestive organs.

• Saliva: Contains enzymes (amylase), lubricates food.

• Regions of Pharynx: Nasopharynx, oropharynx, laryngopharynx.

• Gastric Glands/Intestinal Crypts: Secrete digestive enzymes, acid, hormones.

• Motility: Segmentation (mixing), peristalsis (propulsion).

• Small Intestine Segments: Duodenum, jejunum, ileum.

• Surface Area Adaptations: Circular folds, villi, microvilli.

• GI Hormones: Gastrin, cholecystokinin (CCK), secretin, GIP.

• Enteric Nervous System: Local control of GI function.

• Digestive Enzymes: Amylase, pepsin, lipase, trypsin, etc.

• Emulsification: Bile salts break down fats for digestion.

• Absorption: Monosaccharides, amino acids, fatty acids absorbed via specific mechanisms.

Nutrition and Metabolism

Metabolic Processes

Metabolism encompasses all chemical reactions in the body, including energy production and nutrient processing.

• Metabolic Rate: Energy expenditure; basal metabolic rate (BMR) measured at rest, fasting, thermoneutrality.

• States: Absorptive (fed, insulin-dominated), post-absorptive (fasting, glucagon-dominated).

• Key Terms: Glycogenesis (glucose → glycogen), glycolysis (glucose breakdown), ketogenesis (ketone production), lipogenesis (fat synthesis), lipolysis (fat breakdown), gluconeogenesis (glucose from non-carbs).

• LDL vs. HDL: LDL delivers cholesterol to tissues; HDL removes cholesterol.

• Liver Functions: Metabolism, vitamin storage, detoxification, bilirubin processing.

Urinary System

Structure and Function

The urinary system maintains fluid, electrolyte, and waste balance.

• Organs: Kidneys, ureters, bladder, urethra.

• Nephron: Functional unit; includes glomerulus, tubules, collecting duct.

• Blood Flow: Renal artery → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries/vasa recta → renal vein.

• Cortical vs. Juxtamedullary Nephrons: Differ in location and loop length.

• Juxtaglomerular Apparatus (JGA): Regulates GFR and blood pressure.

• Urine Formation: Filtration (glomerulus), reabsorption, secretion (tubules).

• GFR: Rate of filtration; regulated by autoregulation, hormones.

• Renin-Angiotensin System: Renin → angiotensinogen → angiotensin I → angiotensin II; increases BP.

• Hormones: ADH (water reabsorption), aldosterone (Na+ reabsorption), ANP (inhibits Na+ reabsorption).

• Micturition Reflex: Controls urination; involves autonomic and somatic nerves.

Water, Electrolyte, and Acid-Base Balance

Fluid Compartments and Balance

Body fluids are distributed between extracellular (ECF) and intracellular compartments.

• ECF: Includes interstitial fluid (IF), plasma.

• Water Balance: Intake via food/drink; loss via urine, sweat, feces, respiration.

• Imbalances: Dehydration, hypovolemia, water intoxication, fluid overload; affect osmolarity.

• Hormonal Responses: ADH, aldosterone, ANP adjust water/salt retention.

Acid-Base Balance

• Buffer Systems: Bicarbonate, protein, phosphate buffers.

• Acidosis/Alkalosis: pH below/above normal range.

• Categories: Respiratory/metabolic acidosis/alkalosis; causes include lung/kidney dysfunction, metabolic disturbances.

• Compensation: Respiratory or renal adjustments to restore pH.

Reproductive System

Structure and Function

The reproductive system ensures species continuity through gamete production and hormone regulation.

• Organs: Male (testes, ducts, glands, penis), female (ovaries, ducts, uterus, vagina).

• Hormones: Regulate gametogenesis and reproductive cycles.

• Oogenesis vs. Spermatogenesis: Egg vs. sperm production; differ in timing and outcome.

• Ovarian Cycle: Follicular, ovulation, luteal phases; regulated by FSH, LH, estrogen, progesterone.

• Uterine Cycle: Menstrual, proliferative, secretory phases; coordinated with ovarian cycle.

• Gamete Pathways: Oocyte: ovary → uterine tube → uterus; sperm: epididymis → vas deferens → urethra.

• Meiosis: Two divisions producing haploid gametes; increases genetic variability.