Chapter Four: Membranes and Integument

Classifications of Membranes

Membranes are thin layers of tissue that cover surfaces, line cavities, and divide spaces or organs. They are classified based on their structure, location, and function.

• Mucous membranes: Line body cavities open to the exterior (e.g., digestive, respiratory tracts); secrete mucus for protection and lubrication.

• Serous membranes: Line closed internal body cavities (e.g., pleura, pericardium, peritoneum); secrete serous fluid to reduce friction.

• Cutaneous membrane: The skin; protects underlying tissues and prevents water loss.

• Synovial membranes: Line joint cavities; secrete synovial fluid for joint lubrication.

Structure and Role of the Integument

The integumentary system consists of the skin and its derivatives. It serves as the body's first line of defense and performs multiple vital functions.

• Functions: Protection, sensation, temperature regulation, excretion, vitamin D synthesis.

• Layers of the Skin:

  • Epidermis: Outermost layer; composed of stratified squamous epithelium.

  • Dermis: Middle layer; contains connective tissue, blood vessels, nerves, hair follicles, and glands.

  • Hypodermis (subcutaneous layer): Deepest layer; consists mainly of adipose tissue for insulation and energy storage.

Important Sublayers of the Epidermis

• Stratum basale: Deepest layer; site of cell division (mitosis).

• Stratum spinosum: Provides strength and flexibility.

• Stratum granulosum: Cells begin to die and keratinize.

• Stratum lucidum: Present only in thick skin (palms, soles).

• Stratum corneum: Outermost layer; dead, keratinized cells provide a barrier.

Cell Types in the Epidermis

• Keratinoctyes: Produce keratin for waterproofing and protection.

• Melanocytes: Produce melanin pigment for UV protection.

• Langerhans cells: Immune defense.

• Merkel cells: Sensory receptors for touch.

Epidermal Derivatives and Supporting Structures

• Nails: Protect distal phalanges; made of hard keratin.

• Hair: Provides protection, sensation, and insulation.

• Sweat glands: Eccrine (thermoregulation) and apocrine (scent); excrete waste and regulate temperature.

• Melanin: Pigment responsible for skin color; protects against UV radiation.

• Other skin coloration: Hemoglobin (redness), carotene (yellow/orange); changes may indicate health conditions (e.g., cyanosis for low oxygen).

Burns

• Degrees of Burns:

  • 1st degree: Affects only the epidermis; redness, mild pain.

  • 2nd degree: Involves epidermis and part of dermis; blisters, more severe pain.

  • 3rd degree: Destroys entire skin thickness; may appear white or charred, often painless due to nerve damage.

• Rule of Nines: Used to estimate the percentage of body surface area affected by burns.

• Critical Burn: Generally, burns are considered critical if they cover >10% of body with 3rd degree burns, >25% with 2nd degree, or involve face, hands, feet, or perineum.

Cancer

• Types:

  • Basal cell carcinoma: Most common, least malignant; arises from stratum basale.

  • Squamous cell carcinoma: Arises from stratum spinosum; can metastasize.

  • Melanoma: Cancer of melanocytes; most dangerous, high metastatic potential.

• ABCD Rule for Melanoma Detection:

  • Asymmetry

  • Border irregularity

  • Color variation

  • Diameter >6mm

• Benign vs. Malignant: Benign tumors do not invade or spread; malignant tumors invade tissues and can metastasize.

Chapter Five: Bones

Cells of Bone and Their Functions

• Osteoblasts: Build new bone matrix (bone formation).

• Osteocytes: Mature bone cells; maintain bone tissue.

• Osteoclasts: Break down bone matrix (bone resorption).

Structure of Long Bones

• Diaphysis: Shaft; composed of compact bone.

• Epiphyses: Ends; contain spongy bone and red marrow.

• Metaphysis: Region between diaphysis and epiphysis; contains epiphyseal plate in growing bones.

• Medullary cavity: Central cavity; contains yellow marrow (fat storage).

• Periosteum: Outer fibrous covering; involved in bone growth and repair.

Roles of the Skeletal System

• Support and shape

• Protection of vital organs

• Movement (leverage for muscles)

• Mineral storage (calcium, phosphate)

• Blood cell production (hematopoiesis in red marrow)

• Triglyceride storage (yellow marrow)

Axial vs. Appendicular Skeleton

• Axial skeleton: Skull, vertebral column, rib cage; supports and protects central axis of body.

• Appendicular skeleton: Limbs and girdles; enables movement.

Role of Hyaline Cartilage

• Formation and Development: Provides model for bone formation during endochondral ossification.

• Articular cartilage: Covers ends of bones at joints; reduces friction and absorbs shock.

• Epiphyseal plate: Growth plate; site of lengthwise bone growth in children and adolescents.

Fracture

• Fracture Types: Simple (closed), compound (open), comminuted, greenstick, spiral, impacted, etc.

• Bone Healing: Involves hematoma formation, fibrocartilaginous callus, bony callus, and bone remodeling.

Structure and Location of Osteon/Haversian System and Trabecular (Spongy) Bone

• Osteon (Haversian system): Structural unit of compact bone; consists of concentric lamellae around a central canal.

• Trabecular (spongy) bone: Network of trabeculae; found in epiphyses of long bones and inside flat bones; contains red marrow.

Classification of Bones and Examples

• Long bones: Longer than wide (e.g., femur, humerus).

• Short bones: Cube-shaped (e.g., carpals, tarsals).

• Flat bones: Thin, flat (e.g., sternum, skull bones).

• Irregular bones: Complex shapes (e.g., vertebrae, pelvis).

• Sesamoid bones: Embedded in tendons (e.g., patella).

Joints and Their Actions

• Classification by Movement:

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

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

  • Diarthrosis (synovial joints): Freely movable (e.g., shoulder, knee).

• Categories of Diarthrosis: Ball-and-socket, hinge, pivot, saddle, condyloid, gliding joints.

Diseases of Bone

• Arthritis: Inflammation of joints; types include osteoarthritis (degenerative), rheumatoid arthritis (autoimmune), gouty arthritis (uric acid crystals).

• Osteoporosis: Decreased bone mass; increased fracture risk; common in postmenopausal women and elderly.

• Abnormal Spinal Curvatures: Scoliosis (lateral curve), kyphosis (excessive thoracic curve), lordosis (excessive lumbar curve).

Additional info: Where details were not specified in the original notes, standard academic context and definitions have been provided to ensure completeness and clarity for exam preparation.

Chapter Six: Muscles

Types of Muscle and Their Characteristics

Muscle tissue is specialized for contraction and is essential for movement, posture, and various bodily functions. There are three main types of muscle in the human body, each with distinct characteristics and functions.

• Skeletal Muscle: Voluntary, striated muscle attached to bones; responsible for body movement.

• Cardiac Muscle: Involuntary, striated muscle found only in the heart; responsible for pumping blood.

• Smooth Muscle: Involuntary, non-striated muscle found in walls of hollow organs (e.g., intestines, blood vessels); controls movement of substances within the body.

Properties of Muscle:

• Excitability: Ability to respond to stimuli.

• Contractility: Ability to shorten forcefully.

• Extensibility: Ability to be stretched.

• Elasticity: Ability to return to original length after stretching.

Locations and Purposes:

• Skeletal muscle: Attached to bones; movement, posture, heat production.

• Cardiac muscle: Heart wall; circulates blood.

• Smooth muscle: Walls of organs; moves food, regulates blood flow, etc.

Muscle Terminology

Understanding muscle terminology is essential for describing muscle structure and function.

• Origin: The fixed attachment point of a muscle.

• Insertion: The movable attachment point.

• Agonist: The primary muscle responsible for movement.

• Antagonist: Muscle that opposes the agonist.

• Synergist: Muscle that assists the agonist.

Gross Structure of Muscle

Muscles are organized into bundles and surrounded by connective tissue layers that provide support and transmit force.

• Connective Tissue Coverings:

  • Epimysium: Surrounds the entire muscle.

  • Perimysium: Surrounds bundles of muscle fibers (fascicles).

  • Endomysium: Surrounds individual muscle fibers.

• Arrangement of Tissues: Muscle fibers are grouped into fascicles, which are grouped to form the whole muscle.

• Attachments: Muscles attach to bones via tendons (dense regular connective tissue).

Microscopic Structure

At the microscopic level, muscle fibers contain myofibrils, which are composed of repeating units called sarcomeres—the basic contractile units of muscle.

• Sarcomere: The functional unit of a myofibril, defined by Z-lines; contains thick (myosin) and thin (actin) filaments.

• Myofibrils: Cylindrical structures within muscle fibers, made up of sarcomeres in series.

• Shape, Structure, Actions, Purpose, Arrangement:

  • Shape: Long, cylindrical fibers.

  • Structure: Alternating light (I) and dark (A) bands due to filament arrangement.

  • Action: Contraction via sliding of actin and myosin filaments.

  • Purpose: Generate force and movement.

  • Arrangement: Sarcomeres aligned end-to-end within myofibrils.

• Sliding Filament Theory: Explains muscle contraction as the sliding of thin (actin) filaments past thick (myosin) filaments, shortening the sarcomere.

  • ATP binds to myosin, allowing it to detach from actin.

  • Myosin head hydrolyzes ATP, cocks into position, and binds to a new actin site.

  • Power stroke occurs as myosin pulls actin filament inward.

  Equation:

Naming Conventions of Muscle

Muscles are named based on characteristics such as location, shape, size, direction of fibers, number of origins, and function.

• Examples:

  • Location: Brachialis (arm)

  • Shape: Deltoid (triangle-shaped)

  • Size: Gluteus maximus (largest of the gluteal muscles)

  • Direction: Rectus abdominis (straight fibers)

  • Number of origins: Biceps brachii (two origins)

  • Function: Flexor carpi radialis (flexes wrist)

Energy Sources

Muscle contraction requires energy, primarily in the form of ATP. Muscles use several sources to regenerate ATP during activity.

• Immediate: Stored ATP and creatine phosphate.

• Short-term: Anaerobic glycolysis (breakdown of glucose without oxygen).

• Long-term: Aerobic respiration (oxidative phosphorylation in mitochondria).

Equation for ATP production (Aerobic):

Movement Initiation

Muscle contraction is initiated by signals from the nervous system, transmitted at the neuromuscular junction.

• Neuromuscular Junction: The synapse between a motor neuron and a muscle fiber.

• Neurotransmitters: Chemical messengers (e.g., acetylcholine) released from the neuron to stimulate muscle contraction.

• Ions Needed: Calcium ions (Ca2+) are essential for triggering contraction by enabling actin-myosin interaction.

• Motor Units: A motor neuron and all the muscle fibers it innervates.

  • Small motor units: Fewer fibers per neuron; allow fine, precise movements (e.g., eye muscles).

  • Large motor units: Many fibers per neuron; allow powerful, gross movements (e.g., thigh muscles).

Definition: A motor unit is a single motor neuron and all the muscle fibers it controls.

Why have different sizes? Small motor units provide precise control, while large motor units provide greater force.

Example: The neuromuscular junction uses acetylcholine to transmit the nerve impulse, which leads to the release of Ca2+ from the sarcoplasmic reticulum, initiating contraction.

Additional info: These notes expand on the outline by providing definitions, examples, and context for each topic, ensuring a comprehensive review for Anatomy & Physiology students.