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 brain, ribs protect heart and lungs).

• Movement: Acts as levers for muscles to pull on.

• Mineral Storage: Stores calcium and phosphate ions.

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

• Fat Storage: Yellow marrow stores triglycerides.

Types of Bone Tissue

• Gross Types: Compact bone (dense, forms outer layer) and spongy bone (trabecular, 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: Osteocytes (mature bone cells), osteoblasts (bone-forming), osteoclasts (bone-resorbing), osteoprogenitor cells.

• Nonliving: Extracellular matrix of collagen fibers and hydroxyapatite (calcium phosphate crystals).

Structure of Bone: The Osteon

• Osteon: Cylindrical unit with concentric lamellae around a central (Haversian) canal containing blood vessels and nerves.

• Lacunae: Small spaces housing osteocytes.

• Canaliculi: Tiny channels connecting lacunae for nutrient/waste exchange.

Bone Development and Growth

• Embryonic Bones: Initially composed of hyaline cartilage or fibrous membranes.

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

• Growth: Occurs at epiphyseal plates; stops when plates ossify (influenced by hormones such as sex hormones).

Bone Remodeling

• Continuous process involving osteoblasts and osteoclasts.

• Hormonal Regulation:

  • Calcitonin: Lowers blood calcium by stimulating bone deposition.

  • 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, sternum.

• Appendicular Skeleton: Limbs, pectoral girdle (shoulder), pelvic girdle (hip).

Skull and Hyoid Bone

• Cranial Bones: Enclose the brain.

• Facial Bones: Form the face structure.

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

Vertebral Column and Ribs

• Regions: Cervical (7), thoracic (12), lumbar (5), sacrum, coccyx.

• Intervertebral Discs: Cartilaginous pads between vertebrae.

• Ribs: True (1-7, attach directly to sternum), false (8-10, attach indirectly), floating (11-12, no anterior attachment).

Pectoral and Pelvic Girdles

• Pectoral Girdle: Clavicle and scapula; attaches arms to trunk.

• Pelvic Girdle: Hip bones; supports lower limbs and protects pelvic organs.

Joints

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

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

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

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

• Knee Joint: Complex synovial joint with menisci and ligaments.

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

Muscle Tissue Types and Characteristics

• Skeletal Muscle: Voluntary, striated, multinucleate, 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 Structure Organization

• Whole muscle → fascicle → muscle fiber (cell) → myofibril → myofilament (actin & myosin).

• Connective tissue sheaths: epimysium (whole muscle), perimysium (fascicle), endomysium (fiber).

Sarcomere and Sliding Filament Theory

• Sarcomere: Functional unit; bordered by Z lines; contains actin (thin) and myosin (thick) filaments.

• Sliding Filament Theory: Myosin heads bind to actin, pulling filaments past each other, shortening sarcomere.

• ATP: Required for myosin head detachment and re-cocking.

Role of Calcium, Troponin, and Tropomyosin

• Calcium released from sarcoplasmic reticulum binds to troponin, shifting tropomyosin to expose actin binding sites.

• T-tubules transmit action potential to interior of muscle fiber.

Neuromuscular Junction and Muscle Contraction

• Motor neuron releases acetylcholine (ACh) at neuromuscular junction, triggering muscle action potential.

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

Major Muscles of the Body

• Muscles are named for location, function, shape, or attachments (e.g., biceps brachii, rectus abdominis).

Chapter 7: Blood

Functions and Composition of Blood

• Functions: Transport, regulation, protection.

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

Formed Elements

• Origin: All formed elements arise from hematopoietic stem cells in red bone marrow.

• Erythrocytes (RBCs): Transport oxygen; biconcave, no nucleus; contain hemoglobin; lifespan ~120 days.

• Leukocytes (WBCs): Immune defense; types include neutrophils, lymphocytes, monocytes, eosinophils, basophils.

• Platelets (Thrombocytes): Cell fragments for clotting.

Hemoglobin and RBC Regulation

• Hemoglobin: Protein that binds oxygen; each molecule carries up to 4 O2.

• Erythropoietin (EPO): Hormone from kidneys stimulating RBC production in response to low oxygen.

• RBCs recycled in spleen and liver.

Leukocytes and Platelets

• Leukocytes: Defend against pathogens; classified by appearance and function.

• Platelets: Initiate clotting; form platelet plug and release clotting factors.

Blood Disorders

• Anemia: Reduced oxygen-carrying capacity; types include iron-deficiency, pernicious, sickle-cell anemia.

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

Blood Types and Transfusion

• ABO System: Based on A and B antigens; four types: A, B, AB, O.

• Rh Factor: Positive (+) or negative (−) based on D antigen.

• Agglutination: Clumping of RBCs due to incompatible transfusion.

• Hemolytic Disease of the Newborn: Occurs if Rh− mother carries Rh+ fetus; prevented by RhoGAM injection.

Blood Type	Antigens	Antibodies	Can Donate To	Can Receive From
A	A	Anti-B	A, AB	A, O
B	B	Anti-A	B, AB	B, O
AB	A, B	None	AB	All
O	None	Anti-A, Anti-B	All	O

Hemostasis and Clotting

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

• Clotting Cascade: Prothrombin activator → prothrombin → thrombin → fibrinogen → fibrin.

• Clots dissolve after healing (fibrinolysis).

• Clotting Disorders: Excessive bleeding (hemophilia) or excessive clotting (thrombosis).

Chapter 8: The Cardiovascular System

Components and Functions

• Heart: Pumps blood.

• Blood Vessels: Transport blood (arteries, veins, capillaries).

• Blood: Carries nutrients, gases, wastes.

Blood Vessel Pathway and Features

• Pathway: Heart → arteries → arterioles → capillaries → venules → veins → heart.

• Arteries/arterioles carry oxygen-rich blood (except pulmonary arteries); veins/venules carry oxygen-poor blood (except pulmonary veins).

• Lumen: Central blood-containing space.

• Endothelium: Inner lining of vessels.

Types of Blood Vessels

• Arteries: Thick walls, high pressure, carry blood away from heart.

• Arterioles: Small arteries, regulate flow to capillaries.

• Capillaries: Thin walls for exchange of gases/nutrients.

• Venules: Collect blood from capillaries.

• Veins: Thin walls, low pressure, valves prevent backflow, return blood to heart.

Blood Movement Mechanisms

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

Lymphatic System

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

Major Vessels and Terms

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

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

• Pulse: Rhythmic expansion of artery due to heartbeat.

• Vasoconstriction: Narrowing of vessels; Vasodilation: Widening of vessels.

Heart Structure and Function

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

• Chambers: Right/left atria (receive blood), right/left ventricles (pump blood).

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

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

Blood Flow Pathway

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

Circuits of the Heart

• Pulmonary Circuit: Right heart to lungs and back.

• Systemic Circuit: Left heart to body and back.

• Coronary Circulation: Supplies 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: Coordinate contraction.

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/arteries, lowest in 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.

Lines of Defense

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

• Second Line (Non-specific): Phagocytes, natural killer (NK) cells, interferons, complement proteins, inflammation, fever.

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

First Line Components

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

Second Line Components

• Phagocytes: Engulf pathogens (e.g., neutrophils, macrophages).

• 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 release.

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, IgA, IgM, IgE, IgD.

• Primary vs Secondary Response: Secondary is faster and stronger due to memory cells.

Immunity Types

Type	Natural	Artificial
Active	Infection	Vaccination
Passive	Maternal antibodies	Antibody injection

T Lymphocytes

• Helper T Cells: Activate other immune cells.

• Cytotoxic T Cells: Destroy infected/cancerous 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; first exposure sensitizes, second triggers reaction.

Additional info: Where details were not explicit, standard academic context was added for completeness (e.g., specific muscle and blood vessel names, antibody classes, and immune cell functions).