Exam 2

Tissue Types

• Tissues are classified into four main types: epithelial, connective, muscle, and nervous.
• Epithelial tissues cover and line surfaces, illustrated by the skin.
• Connective tissues function as joiners, binding and supporting various other tissues.
• Muscle tissues have the ability to contract for movement.
• Nervous tissues create and transmit electrical impulses.

Extracellular Matrix

• Consists of ground substance (extracellular fluid) rich in nutrients, water, and ions.
• Contains protein fibers:
  • Collagen fibers provide strength and structure to tissues.
  • Elastic fibers allow tissues to stretch and recoil.
  • Reticular fibers offer delicate support.

Epithelial Tissues

• Characterized by minimal extracellular matrix and tightly packed cells forming sheets.
• Exhibits polarity: one end connects to basement membranes, while the free end is termed the apical surface.
• Avascular in nature (lacks blood vessels), cells undergo mitosis and regenerate quickly.
• Functions include diffusion, filtration, secretion, absorption, and protection.
• Classified by cell layers as simple (one layer) or stratified (multiple layers) and by cell shape: squamous (scale-like), cuboidal (cube-like), and columnar (column-like).

Types of Epithelial Tissues

• Simple squamous epithelium facilitates rapid diffusion (e.g., alveoli of lungs).
• Simple cuboidal epithelium is involved in secretion and absorption (e.g., kidney tubules).
• Simple columnar epithelium aids in absorption and secretion (e.g., GI tract).
• Pseudostratified columnar epithelium appears stratified but is a single layer, ciliated (e.g., respiratory tract).
• Stratified squamous epithelium provides protection with multiple layers; can be keratinized (e.g., skin) or non-keratinized (e.g., mouth, throat).
• Transitional epithelium responds to stretching, found only in the urinary system (e.g., bladder).

Connective Tissue

• Comprises significant extracellular matrix and exhibits varied blood supply and functions.
• Functions include protection, support, binding, insulation, and transport.
• Types include:
  • Areolar connective tissue underlies epithelia and cushions organs.
  • Adipose tissue is composed of fat cells (adipocytes) that provide insulation and energy storage.
  • Dense regular tissue connects muscles to bones (e.g., tendons) with poor blood supply.
  • Dense irregular tissue offers multi-directional strength (e.g., skin).
  • Cartilage consists of chondrocytes in lacunae, with types:
    • Hyaline cartilage, smooth, found between bones.
    • Elastic cartilage, flexible (e.g., external ear).
    • Fibrocartilage, supportive (e.g., intervertebral discs).
  • Bone contains osteocytes in a calcified matrix, providing support and protection.
  • Blood consists of red and white blood cells in plasma, transporting gases, nutrients, and wastes.

Muscle Tissue

• Contains minimal extracellular matrix and is highly vascularized.
• Types include:
  • Skeletal muscle is long, striated, voluntary, and attached to bones.
  • Smooth muscle features spindle-shaped cells, involuntary, and found in hollow organ walls.
  • Cardiac muscle is striated, involuntary, found only in the heart, propelling blood.

Nervous Tissue

• Contains a moderate amount of extracellular matrix and is vascularized.
• Composed of two main cell types:
  • Neurons, which conduct electrical signals.
  • Glial cells, supporting neurons, making up 90% of the tissue.

Integumentary System

• Comprises the skin, hair, and nails, serving as the body’s first line of defense.
• Functionally involved in protection, temperature regulation, and sensation.### Integumentary System Functions
• Regulation of body temperature, excretion, and sensory reception.
• Conversion of cholesterol to Vitamin D, crucial for calcium absorption.

Skin Structure

• Composed of two main layers: Epidermis (outer) and Dermis (inner).

Epidermis

• Thin layer (millimeters thick) primarily consisting of four to five layers.
• Stratum Basale (Germinativum):
  • Bottom-most layer containing melanocytes for skin coloration and UV protection.
  • Houses Merkel cells for light touch detection and keratinocytes which produce keratin.
• Stratum Spinosum:
  • Contains Langerhans cells, a type of white blood cell, that detect foreign substances.
• Stratum Granulosum:
  • Cells begin to flatten and die, involved in keratin production.
• Stratum Lucidum:
  • Only present in thick skin areas such as palms and soles, lies between Granulosum and Corneum.
• Stratum Corneum:
  • Composed of dead keratinocytes, acts as a barrier; sheds approximately 40 pounds of skin cells in a lifetime.

Dermis

• Thicker than the epidermis, consists of two layers:
  • Papillary Layer:
    • Made of areolar connective tissue; contains capillaries, nerve endings, and Meissner's corpuscles for light touch.
  • Reticular Layer:
    • Comprised of dense irregular connective tissue; contains blood vessels, Pacinian corpuscles for deep touch, hair follicles, and glands (sebaceous and sudoriferous).
    • Glands can be:
      • Sebaceous: Produce oil.
      • Sudoriferous:
        • Eccrine: For temperature regulation, found over large body surfaces.
        • Apocrine: Located in armpits and groin, associated with stress and nervousness.

Skin Coloration

• Influenced by melanin, hemoglobin (oxygen-carrying pigment in blood), and carotene (found in carrots and egg yolks).

Burns Classification

• 1st Degree: Affects only the epidermis.
• 2nd Degree: Involves epidermis and part of the dermis, may cause blisters.
• 3rd Degree: Extends through the epidermis and dermis and beyond.

Skeletal System Functions

• Provides protection, support, movement with muscles, mineral storage, and hematopoiesis (blood cell formation).

Bone Cells

• Osteocytes: Mature bone cells.
• Osteoblasts: Cells that build bone.
• Osteoclasts: Cells that break down bone, releasing calcium and phosphorus.

Determinants of Bone Growth

• Influenced by heredity, hormones, nutrition, exercise, and injury.

Classification of Bones

• Long Bones: Longer than wide (e.g., femur, radius).
• Short Bones: About equal in length and width (e.g., carpals, tarsals).
• Sesamoid Bones: Special type developed within tendons (e.g., patella).
• Flat Bones: Thin and broad (e.g., scapula, cranium).
• Irregular Bones: Unique shapes (e.g., vertebrae, maxilla).

Structure of Long Bones

• Epiphysis: Ends of the bone.
• Diaphysis: The shaft or core of the bone.
• Epiphyseal Line: Growth plate between epiphysis and diaphysis.
• Medullary Cavity: Hollow area within bone containing yellow bone marrow (fat).
• Red Bone Marrow: Found in epiphysis, involved in blood cell production.
• Articular Cartilage: Thin layer at end of bones preventing friction.

Microscopic Structure of Bone

• Osteon: Structural unit of bone with a central canal (Haversian canal) containing blood vessels.
• Lacunae: Spaces containing osteocytes.
• Canaliculi: Channels connecting lacunae to blood supply.

Development of Bone

• Ossification: Development process before and after birth.
• Intramembranous: Formation within a membrane, primarily for flat bones.
• Endochondral: Formation within cartilage, used for most other bones.

Bone Remodeling

• Balanced process of bone formation and resorption controlled by hormones like parathyroid hormone and calcitonin.

Joints Classification

• Functional:
  • Synarthroses: Immovable joints (e.g., skull sutures).
  • Amphiarthroses: Slightly movable (e.g., pubic symphysis).
  • Diarthroses: Freely movable (e.g., knee, elbow).
• Structural:
  • Fibrous: Connected by fibrous tissue (e.g., sutures).
  • Cartilaginous: Connected by cartilage (e.g., intervertebral discs).
  • Synovial: Fluid-filled joints allowing movement; examples include hinge and ball-and-socket joints.