Tissues and Membranes

Terminology and Word Roots

Understanding medical terminology is essential for studying anatomy and physiology. Many terms are derived from Greek and Latin roots, prefixes, and suffixes that describe tissue types, cell functions, and pathological conditions.

• aden/o: gland

• blast/o: immature cell

• carcin/o: cancer, cancerous

• chondr/o: cartilage

• cyt/o: cell

• fibr/o: fibers

• hist/o, histi/o: tissue

• oste/o: bone

• plas/o: formation, development

• -blast: immature

• -cyte: cell

• -oma: mass, tumor

• -plasia, -plasm: formation, growth

• meta-: beyond (e.g., metastasis)

Abbreviations: bx (biopsy), CA (cancer), chem (chemotherapy), CIS (carcinoma in situ), NED (no evidence of disease), prot (protocol)

Types of Tissues

Tissues are groups of cells with similar structure and function, combined to form organs and membranes. The four basic types are epithelial, connective, muscle, and nervous tissue.

Epithelial Tissue

Epithelial tissue covers surfaces, lines cavities, and forms glands. Cells are tightly joined, avascular, and attached to connective tissue via a basement membrane. Classification is based on cell layers and cell shape.

• Simple: one layer

• Stratified: multiple layers

• Squamous: flat cells

• Cuboidal: cube-shaped cells

• Columnar: tall, narrow cells

Stratified Squamous Epithelium

Multiple layers of closely packed cells, with the outermost layer flattened. Found in the epidermis and mucous membranes, providing protection against microorganisms.

• Function: Protection (barrier)

Simple Cuboidal Epithelium

Single layer of cube-shaped cells, often forming tubules (glands). Specialized for secretion.

• Function: Secretion

Simple Columnar Epithelium

Single layer of elongated, cylindrical cells lining the stomach, intestines, respiratory, and female reproductive tracts. Specialized for secretion and absorption.

• Goblet Cells: Produce mucus for lubrication

• Cilia: Move substances over cell surface

• Microvilli: Increase surface area for absorption

Pseudostratified Columnar Epithelium

Appears multi-layered due to irregular placement of nuclei, but is actually a single layer. Lines air passages and male reproductive system.

• Function: Secretion and movement of mucus

Transitional Epithelium

Stratified sheet with varying cell shapes, capable of stretching. Found in the bladder.

• Function: Allows stretching under tension

Intercellular Connections

Specialized junctions connect epithelial cells:

• Desmosomes: Anchoring junctions for mechanical stress

• Gap Junctions: Channels for communication

• Tight Junctions: Impermeable barriers

Connective Tissue

Connective tissue is the most abundant and varied tissue, providing support, protection, and transport. It consists of cells and an extracellular matrix made of fibers (collagen, elastin, reticular) and ground substance.

• Fibrous (loose, dense)

• Bone

• Cartilage

• Blood

Loose Fibrous: Areolar Tissue

Contains tissue fluid, collagen, and elastin. Fibroblasts and macrophages are present. Acts as packing material under skin and mucous membranes.

Loose Fibrous: Adipose Tissue

Mainly fat cells, stores energy, insulates, and cushions organs.

Loose Fibrous: Reticular Tissue

Three-dimensional web of reticular fibers, holds blood cells. Found in bone marrow, spleen, and lymph nodes.

Dense Fibrous Tissue

Primarily collagen fibers and fibroblasts, providing strength and flexibility. Found in tendons, ligaments, and dermis.

Bone Tissue

Hard matrix with few cells. Osteoblasts form bone, osteocytes are mature bone cells. Two types: compact (dense, stores calcium, supports body) and spongy (contains red marrow, forms blood cells).

Spongy Bone

Located within the hollow center of compact bone, contains red bone marrow and reticular fibers.

Cartilage

Strong, flexible matrix with few cells. Chondroblasts are active, chondrocytes are mature. Types include hyaline, fibrocartilage, and elastic cartilage.

• Hyaline: Shiny, translucent, ends of bones

• Fibrocartilage: Strongest, found in knee and vertebrae

• Elastic: Flexible, found in ears

Blood

Liquid matrix, no fibers. Contains various cells produced in red bone marrow. Functions in transport and protection.

Muscle Tissue

Muscle tissue is specialized for contraction and movement. Contains contractile fibers and is well vascularized.

• Skeletal Muscle: Striated, voluntary, attaches to bone, produces movement and heat

• Cardiac Muscle: Striated, involuntary, found in heart, contracts to pump blood

• Smooth Muscle: Non-striated, involuntary, forms walls of blood vessels and hollow organs

Nervous Tissue

Nervous tissue transmits impulses for sensation, movement, regulation, learning, and memory. Main cell is the neuron, supported by glial cells.

• Neuron: Cell body (nucleus), axon (away from cell body), dendrites (toward cell body)

Membranes

Membranes are combinations of tissues forming thin sheets. Types include:

• Cutaneous: Skin, stratified squamous epithelium over dense connective tissue

• Serous: Moist membrane lining closed cavities and covering organs; secretes serous fluid

• Mucous: Lines tracts opening to exterior; moist, traps particles, lubricates

• Synovial: Lines spaces between bones and joints; secretes synovial fluid

Tissue Repair and Aging

Tissue Repair Steps

1. Inflammation: Capillaries become permeable, clot forms

2. Organization: Granulation tissue restores blood supply, fibroblasts generate collagen

3. Regeneration or Fibrosis: Tissue replaced by same type (regeneration) or scar tissue (fibrosis)

Effects of Aging

• Tissue repair slows

• Tissue becomes thinner, loses elasticity

• Glands less active

• Bones weaken

• Muscle and nervous tissue atrophy

Neoplasms and Cancer

A neoplasm is a mass arising from normal tissue. Benign tumors grow slowly and are not cancerous; malignant tumors (cancer) grow rapidly, can metastasize, and are life-threatening.

• Carcinomas: From epithelial tissue (90%)

• Sarcomas: From connective tissue (5%)

• Mixed Tissue Tumors: From both (rare)

Cancer Staging

Warning Signals of Cancer

• Change in bowel/bladder habits

• Sore that does not heal

• Unusual bleeding/discharge

• Lump in breast or other body part

• Chronic indigestion/difficulty swallowing

• Obvious changes in wart/mole

• Persistent coughing/hoarseness

Cancer Treatments and Prevention

• Surgery: Remove or prevent

• Radiation Therapy: Target tumor

• Chemotherapy: Drugs target rapidly dividing cells

• Immunotherapy: Stimulate immune system

• Prevention: Self-exams, regular physicals, healthy lifestyle, avoid risk factors