Integumentary system

Chapter 5 Tissue Organization Essentials

Identify each tissue, explain how its structure fits its job, and name a location.

The big picture

Tissue = cells + extracellular material working together. Histology = study of tissues. An organ combines two or more tissue types.

Epithelial: covers, lines, secretes. Connective: supports, binds, protects, stores and transports. Muscle: contracts for movement. Nervous: receives, processes and sends signals.

Read an epithelium

Tightly packed, little matrix, no blood vessels, rapid renewal. Apical = exposed surface; basal = attached to basement membrane. Nutrients diffuse from nearby tissue.

Name = layers + apical cell shape. Simple = one layer (exchange/absorption/secretion); stratified = multiple layers (protection). Squamous = flat; cuboidal = boxlike; columnar = tall.

Pseudostratified: looks layered, but every cell touches the basement membrane. Transitional: stratified tissue that changes shape with stretch.

Microvilli increase surface area; cilia move material. Goblet cells secrete mucin, which forms mucus with water.

Structure and function matches

Simple squamous: thin exchange barrier; alveoli and vessels (endothelium); serous lining (mesothelium).

Simple cuboidal: absorption/secretion; kidney tubules and gland ducts.

Simple columnar: absorption/secretion; digestive tract. Ciliated form moves the oocyte in uterine tubes.

Ciliated pseudostratified: clears mucus; trachea.

Stratified squamous: resists abrasion. Keratinized = epidermis; nonkeratinized = moist mouth/esophagus.

Transitional: stretches; bladder/ureters. Stratified cuboidal/columnar: protection/secretion in some ducts.

Know where gland products go

Endocrine: ductless; hormones enter blood. Exocrine: products reach a surface, usually through ducts; goblet cells are a unicellular exception.

Merocrine = exocytosis; apocrine = apical portion released; holocrine = whole cell breaks down. These describe exocrine secretion.

Simple/compound = unbranched/branched duct. Tubular/acinar = tube/sac secretory region.

Connective tissue: the matrix matters

Matrix = fibers + ground substance. Fibroblasts make matrix. Collagen resists pulling; elastic fibers stretch/recoil; reticular fibers form a supporting mesh.

Loose: areolar packs/supports; adipose stores energy, cushions and insulates; reticular supports lymph nodes/spleen.

Dense: regular has parallel collagen for one-direction tension (tendons: muscle to bone; ligaments: bone to bone). Irregular resists many directions (dermis). Elastic permits recoil (large arteries).

Cartilage: chondrocytes in lacunae; avascular, so heals slowly. Hyaline = smooth support (trachea/joint surfaces); fibrocartilage = compression resistance (discs/menisci); elastic = flexibility (ear/epiglottis).

Bone: mineralized matrix; osteocytes in lacunae; support, protection and mineral storage. Blood: fluid matrix (plasma); red cells carry gases, white cells defend, platelets help clot. Lymph returns tissue fluid to blood and carries immune cells.

Distinguish muscle and nervous tissue

Skeletal: striated, long, many nuclei; voluntary; moves skeleton. Cardiac: striated, branched, intercalated discs; involuntary; pumps blood. Smooth: no striations, spindle-shaped; involuntary; hollow organ walls.

Neurons signal: dendrites receive, cell body houses nucleus, axon sends. Glia support/protect neurons.

Membranes and the skin connection

Mucous: passages open to outside. Serous: closed cavities; parietal lines wall, visceral covers organ; fluid reduces friction. Cutaneous: skin. Synovial: joint lining; connective tissue, no true epithelium.

Skin: epidermis = keratinized epithelium; dermis = connective tissue. Hypodermis lies below skin. Epidermal layers, deep to superficial: basale, spinosum, granulosum, lucidum (thick skin only), corneum. Eccrine sweat cools; sebaceous glands make sebum.

Development and tissue change

Ectoderm: epidermis/nervous tissue. Mesoderm: muscle and most connective tissue. Endoderm: much digestive/respiratory epithelium.

Hypertrophy = bigger cells; hyperplasia = more cells; atrophy = shrinkage; metaplasia = cell-type replacement; dysplasia = abnormal development; neoplasia = uncontrolled growth; necrosis = cell/tissue death.