Human Biology Study Guide: Skeleton, Muscles, Blood, Cardiovascular, and Immune Systems

Chapter 5: The Skeletal System

Functions of the Skeleton

• Support: Provides structural framework for the body.

• Protection: Shields vital organs (e.g., skull protects the brain, rib cage protects the heart and lungs).

• Movement: Serves as levers for muscles to act upon.

• Mineral Storage: Stores calcium and phosphate ions.

• Blood Cell Production: Houses red bone marrow for hematopoiesis.

• Fat Storage: Yellow bone marrow stores triglycerides.

Types of Bone Tissue

• Gross Types: Compact bone (dense, forms outer layer) and spongy bone (porous, found at ends of long bones and inside flat bones).

• Microscopic Types: Osteons (Haversian systems) in compact bone; trabeculae in spongy bone.

Components of Bone

• Living: Osteoblasts (build bone), osteocytes (maintain bone), osteoclasts (break down bone).

• Nonliving: Extracellular matrix of collagen fibers and mineral salts (mainly hydroxyapatite).

Structure of Bone: The Osteon

• Osteon: Cylindrical unit with concentric lamellae (layers), central (Haversian) canal, lacunae (spaces for osteocytes), canaliculi (tiny canals for nutrient/waste exchange).

• Appearance: Resembles tree rings under microscope.

Bone Development and Growth

• Embryonic Bones: Initially composed of hyaline cartilage.

• Ossification: Replacement of cartilage by bone (endochondral ossification).

• Growth: Occurs at epiphyseal (growth) plates; stops when plates ossify (usually after puberty).

Bone Remodeling and Hormonal Control

• Remodeling: Continuous process of bone resorption and formation.

• Hormones:

  • Calcitonin: Lowers blood calcium by stimulating bone formation.

  • Parathyroid hormone (PTH): Raises blood calcium by stimulating bone resorption.

  • Estrogen, growth hormone, thyroid hormones, sex hormones: Regulate growth and maintenance.

Divisions of the Skeleton

• Axial Skeleton: Skull, vertebral column, rib cage.

• Appendicular Skeleton: Limbs, pectoral and pelvic girdles.

Skull and Associated Bones

• Cranial Bones: Enclose the brain (e.g., frontal, parietal, occipital).

• Facial Bones: Form the face (e.g., maxilla, mandible).

• Hyoid Bone: Unique; does not articulate with other bones; supports tongue.

Vertebral Column and Ribs

• Regions: Cervical (7), thoracic (12), lumbar (5), sacral, coccygeal.

• Intervertebral Discs: Cushion vertebrae.

• Ribs: True (attach directly to sternum), false (indirect or no attachment), floating (no anterior attachment).

Pectoral and Pelvic Girdles

• Pectoral Girdle: Clavicle and scapula; attaches upper limbs.

• Pelvic Girdle: Hip bones; attaches lower limbs, supports weight.

Joints

• Fibrous Joints: Immovable (e.g., sutures of skull).

• Cartilaginous Joints: Slightly movable (e.g., intervertebral discs).

• Synovial Joints: Freely movable; contain synovial fluid (e.g., knee, shoulder).

• Parts of Synovial Joints: Articular cartilage, joint capsule, synovial membrane, ligaments.

• Knee Joint: Includes menisci, cruciate ligaments, patella.

Types of Movement

• Flexion/Extension: Decreasing/increasing angle between bones.

• Adduction/Abduction: Movement toward/away from midline.

• Rotation/Circumduction: Turning around axis/moving in a circle.

• Supination/Pronation: Rotating forearm to turn palm up/down.

Chapter 6: The Muscular System

Characteristics and Types of Muscle Tissue

• Skeletal Muscle: Voluntary, striated, multinucleated, attached to bones.

• Cardiac Muscle: Involuntary, striated, branched, found in heart.

• Smooth Muscle: Involuntary, non-striated, found in walls of organs.

Functions of Skeletal Muscles

• Movement, posture, heat production, joint stabilization.

Muscle Terminology

• Synergistic Muscles: Work together for movement.

• Antagonistic Muscles: Oppose each other's action.

• Tendon: Connects muscle to bone.

• Origin: Fixed attachment point.

• Insertion: Movable attachment point.

Muscle Organization

• Whole muscle → fascicles → muscle fibers (cells) → myofibrils → myofilaments (actin, myosin).

• Connective Tissue Sheaths: Epimysium (around muscle), perimysium (around fascicle), endomysium (around fiber).

Sarcomere Structure and Muscle Contraction

• Sarcomere: Functional unit; contains Z lines, actin (thin), myosin (thick).

• Sliding Filament Theory: Myosin heads bind to actin, pulling filaments past each other; ATP required.

• During contraction, sarcomere shortens; during relaxation, returns to original length.

Role of Calcium, Troponin, and Tropomyosin

• Calcium released from sarcoplasmic reticulum binds to troponin, causing tropomyosin to move and expose binding sites on actin.

• T-tubules: Transmit action potential into muscle fiber.

Neuromuscular Junction and Signal Transmission

• Motor neuron releases acetylcholine (ACh) at neuromuscular junction.

• ACh binds to receptors on muscle fiber, triggering action potential and contraction.

Motor Units

• Motor Unit: One motor neuron and all muscle fibers it innervates.

Major Muscles of the Body

• Examples: biceps brachii (arm flexion), quadriceps femoris (knee extension), deltoid (shoulder abduction).

Chapter 7: Blood

Functions and Composition of Blood

• Functions: Transport (gases, nutrients, wastes), regulation (pH, temperature), protection (immune response, clotting).

• Composition: Plasma (~55%), formed elements (~45%).

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

Origin and Types of Formed Elements

• All formed elements originate from hematopoietic stem cells in red bone marrow.

• Leukocytes: Granulocytes (neutrophils, eosinophils, basophils), agranulocytes (lymphocytes, monocytes).

Red Blood Cells (RBCs)

• Function: Transport oxygen (via hemoglobin), some CO2.

• Features: Biconcave, no nucleus, flexible.

• Hemoglobin: Protein with iron; binds O2.

• Life Span: ~120 days; recycled in spleen and liver.

• Erythropoietin: Hormone from kidneys; stimulates RBC production.

White Blood Cells (WBCs)

• Function: Defense against pathogens.

• Categories: Granulocytes (neutrophils, eosinophils, basophils), agranulocytes (lymphocytes, monocytes).

• Each type has unique appearance and function (e.g., neutrophils: phagocytosis; lymphocytes: immune response).

Platelets

• Function: Blood clotting (hemostasis).

• Features: Cell fragments, no nucleus.

Blood Disorders

• Anemia: Low RBCs or hemoglobin; causes include iron deficiency, sickle-cell (abnormal hemoglobin).

• Leukemia: Cancer of WBCs; treated with chemotherapy, bone marrow transplant.

Blood Types and Transfusion

• ABO System: Types A, B, AB, O; based on antigens on RBCs.

• Rh Factor: Positive (+) or negative (-).

• Antibodies: Present in plasma; cause agglutination if incompatible blood is transfused.

• Hemolytic Disease of the Newborn: Occurs if Rh- mother has Rh+ baby; prevented by RhoGAM.

Blood Type	Antigens on RBC	Antibodies in Plasma	Can Receive From
A	A	Anti-B	A, O
B	B	Anti-A	B, O
AB	A, B	None	A, B, AB, O
O	None	Anti-A, Anti-B	O

Hemostasis and Clotting

• Three Steps: Vascular spasm, platelet plug formation, coagulation.

• Clotting Factors: Prothrombin activator converts prothrombin to thrombin; thrombin converts fibrinogen to fibrin.

• Clots dissolve after healing (fibrinolysis).

Blood Clotting Disorders

• Hemophilia: Deficiency of clotting factors; excessive bleeding.

• Thrombosis: Unwanted clot formation.

Chapter 8: The Cardiovascular System

Components and Functions

• Components: Heart, blood vessels, blood.

• Functions: Transport, regulation, protection.

Pathway of Blood and Blood Vessels

• Arteries → arterioles → capillaries → venules → veins.

• Arteries/arterioles: usually oxygen-rich; veins/venules: usually oxygen-poor (except pulmonary circuit).

Structure of Blood Vessels

• Lumen: Central cavity.

• Endothelium: Inner lining.

• Arteries: Thick, elastic walls; high pressure.

• Veins: Thinner walls, valves; low pressure.

• Capillaries: One cell thick; site of exchange.

Major Blood Vessels

• Aorta: Largest artery; carries blood from heart to body.

• Vena Cavae: Largest veins; return blood to heart.

Blood Movement Mechanisms

• Muscle contractions, valves, pressure gradients help move blood, especially in veins against gravity.

Lymphatic System

• Returns excess tissue fluid to bloodstream; involved in immune defense.

Heart Structure and Function

• Layers: Pericardium (outer), myocardium (muscle), endocardium (inner).

• Chambers: Right/left atria (upper), right/left ventricles (lower).

• Valves: Right AV (tricuspid), left AV (bicuspid/mitral), pulmonary and aortic semilunar valves.

• Septum: Divides right and left sides.

• Heart Sounds: "Lub-dup" from valve closures.

Blood Flow Through the Heart

• Right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body.

Pulmonary and Systemic Circuits

• Pulmonary: Heart to lungs and back (right side).

• Systemic: Heart to body and back (left side).

Coronary Circulation

• Supplies blood to heart muscle itself.

Cardiac Cycle

• Systole: Contraction phase; blood ejected.

• Diastole: Relaxation phase; chambers fill.

Cardiac Conduction System

• SA Node: Pacemaker; initiates heartbeat.

• AV Node, bundle of His, Purkinje fibers: Conduct impulses through heart.

Electrocardiogram (ECG/EKG)

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

Blood Pressure

• Definition: Force of blood against vessel walls.

• Sphygmomanometer: Device to measure blood pressure.

• Systolic: Pressure during contraction; Diastolic: Pressure during relaxation.

• Pressure highest in aorta, decreases through arteries, arterioles, capillaries, veins.

Chapter 9: The Immune System and Mechanisms of Defense

Key Terms

• Pathogen: Disease-causing organism.

• Antigen: Substance that triggers immune response.

• Cancer Cells: Abnormal cells with uncontrolled growth.

Three Lines of Defense

• First Line (Non-specific): Physical and chemical barriers (skin, mucous membranes, secretions).

• Second Line (Non-specific): Internal defenses (phagocytes, NK cells, inflammation, fever, complement, interferons).

• Third Line (Specific): Adaptive immunity (lymphocytes, antibodies, memory).

First Line Components

• Skin, mucous membranes, tears, saliva, stomach acid.

Second Line Components

• Phagocytes: Engulf pathogens.

• Natural Killer (NK) Cells: Destroy infected/cancerous cells.

• Interferons: Proteins that inhibit viral replication.

• Complement: Proteins that enhance immune response.

• Pyrogens: Cause fever.

• Inflammation: Redness, heat, swelling, pain; caused by histamine and other chemicals.

Third Line: Adaptive Immunity

• MHC (Major Histocompatibility Complex): Cell surface proteins for self-recognition.

• Lymphocytes: B cells (produce antibodies), T cells (cell-mediated immunity).

• Effector Cells: Act immediately; Memory Cells: Provide long-term immunity.

• Antibodies: Proteins that bind antigens; classes include IgG, IgM, IgA, IgE, IgD.

• Memory B Cells: Enable rapid response to future exposures.

Primary vs Secondary Immune Response

• Primary: First exposure; slower, weaker response.

• Secondary: Subsequent exposure; faster, stronger due to memory cells.

Active and Passive Immunity

• Active: Body produces its own antibodies (natural: infection; artificial: vaccination).

• Passive: Antibodies received from another source (natural: mother to baby; artificial: injection of antibodies).

T Lymphocytes

• Helper T Cells: Activate other immune cells.

• Cytotoxic T Cells: Destroy infected cells.

• Regulatory T Cells: Suppress immune response.

• Memory T Cells: Provide long-term immunity.

Immune Disorders

• Autoimmune Disease: Immune system attacks self (e.g., lupus, rheumatoid arthritis).

• Allergy: Overreaction to harmless antigen (allergen); first exposure sensitizes, second triggers reaction.

Example: Hemolytic Disease of the Newborn

• Occurs when Rh- mother has Rh+ fetus; maternal antibodies attack fetal RBCs in subsequent pregnancies.

• Prevented by RhoGAM injection to mother.

Additional info:

• For all systems, homeostasis and feedback mechanisms are crucial for normal function.

• Tables and diagrams are often used to compare cell types, blood types, and immune responses.