Epithelial Tissues Overview

Epithelial Tissues

• Simple Squamous: Single layer of flat cells; facilitates diffusion and filtration; found in lungs (alveoli), blood vessels (endothelium), and kidneys.
• Simple Columnar: Single layer of tall cells; absorption and secretion (mucus, enzymes); lines stomach, intestines, and uterine tubes.
• Simple Cuboidal: Single layer of cube-shaped cells; secretion and absorption; found in kidney tubules, glands, and ducts.
• Pseudostratified Columnar: Single layer of cells of varying heights; secretion and mucus movement; lines trachea and upper respiratory tract.
• Stratified Squamous: Multiple layers of cells, surface cells are flat; protection against abrasion; located in skin, mouth, esophagus, and vagina.
• Stratified Columnar: Multiple layers; protection and secretion; found in male urethra and ducts of some glands.
• Transitional: Multiple layers; stretches to accommodate fluid volume changes; lines bladder, ureters, and part of urethra.

Connective Tissues

• Areolar: Binds organs, provides nutrients; located under epithelial tissues and around organs.
• Dense Regular: Attaches muscles to bones or bones to bones; found in tendons and ligaments.
• Dense Irregular: Provides strength and resists tension in multiple directions; in dermis of skin and fibrous capsules of organs.
• Adipose: Stores fat, insulates, cushions; under skin and around organs.
• Hyaline Cartilage: Supports, reinforces, cushions; found at ends of long bones, nose, and trachea.
• Fibrocartilage: Absorbs compressive shock; in intervertebral discs and pubic symphysis.
• Elastic Cartilage: Maintains structure while allowing flexibility; in external ear and epiglottis.
• Spongy Bone: Supports, protects, houses bone marrow; in ends of long bones and inside vertebrae.
• Compact Bone: Provides support, protection, and levers for movement; outer layer of bones.
• Blood: Transports gases, nutrients, wastes; circulates throughout the body in blood vessels.

Collagen and Elastin

• Collagen: Strong, flexible, resistant to stretching; provides structural support and tensile strength.
• Elastin: Allows tissues to stretch and recoil; provides elasticity to skin, blood vessels, and lungs.

Loose Connective and Adipose Tissue Relationship

• Adipose tissue is a specialized form of loose connective tissue, dominated by adipocytes (fat cells).

Cartilage Characteristics

• Flexible, avascular tissue; composed of chondrocytes in a matrix of collagen and proteoglycans; provides support, cushioning, and allows smooth joint movements.

Bone vs. Cartilage Healing

• Bone heals faster than cartilage due to its vascularization (blood supply).

Muscle Tissues

• Skeletal: Long, striated fibers, voluntary control; movement, posture; attached to bones.
• Cardiac: Branched, striated fibers, involuntary control; pumps blood; located in the heart.
• Smooth: Non-striated, spindle-shaped cells, involuntary control; moves substances through hollow organs; found in walls of digestive tract and blood vessels.

Neurons and Nervous System

• Neurons transmit electrical impulses; receive sensory input, integrate information, send motor output.
• Major neuron-containing organs: brain and spinal cord.

Cancer and Epithelial Tissue

• Most adult cancers originate in epithelial tissue (adenomas or carcinomas) due to frequent cell division and regeneration.

Epidermis Layers (from deep to superficial)

• Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (thick skin only), stratum corneum.

Skin Pigments

• Melanin and carotene.

Dermis Components

• Papillary layer and reticular layer.

Integumentary Accessory Structures

• Hair, nails, sweat glands, sebaceous glands.

Major Exocrine Glands in Skin

• Sweat glands and sebaceous glands.

Vitamin D Deficiency and Bone Problems

• Limited sun exposure can cause vitamin D deficiency, leading to bone problems (e.g., osteoporosis).

Sebaceous Secretion Functions

• Lubricates and moisturizes skin and hair; prevents water loss; protects against bacterial infections.

Deodorants and Apocrine Sweat Glands

• Deodorants mask the odor from apocrine sweat glands (armpits, groin).

Puberty and Sebaceous Glands

• Sebaceous gland activity increases during puberty due to hormonal changes, potentially causing acne.

Skin Regeneration

• Stem cells in the stratum basale replace damaged cells; dermis's rich blood supply aids healing.

Carotenemia

• Yellow-orange skin complexion due to excessive carotene intake from diet (harmless).

Cartilage Types and Locations

• Hyaline: Ends of long bones, nose, trachea, larynx, ribs.
• Elastic: External ear, epiglottis.
• Fibrocartilage: Intervertebral discs, pubic symphysis, menisci of the knee.

Bone Classification and Examples

• Long bones: Humerus, Ulna.
• Flat bones: Ribs.
• Irregular bones: Vertebrae.
• Short bones: Lunate (carpal bone).

Axial Skeleton Components

• Vertebral column, thoracic cage (rib cage).

Cranial Bones

• Frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.

Bone Names

• Forehead: Frontal bone.
• Cheekbone: Zygomatic bone.
• Lower jaw: Mandible.
• Upper jaw: Maxilla.