2. Cells & Tissues

Epithelium characteristics & function

1. cellularity - barrier & lining

2. polarity - directional transport

3. attachment - support & regulation

4. avascularity - thin protective layers

5. regeneration - rapid repair

6. specialized contacts - integrity & communication

Classifcation of layers of lining epithelium

1. Simple epithelium - single layer of cells, specialized for absorption, secretion, filtration

2. Stratified epithelium - multiple layers, protective against friction & mechanical stress

3. Pseudostratified epithelium - appears multilayered but all cells touch the basement membrane, often ciliated, found in respiratory tract

4. Transitional epithelium - multiple layers with cells that change shape, allows stretching (eg, urinary bladder)

All epithelium types (9)

1. simple squamous - flat, thing cells; alveoli, capillaries; diffusion, filtration

2. simple cuboidal - cube-shaped; kidney tubules; secretion & absorption

3. simple columnar - tall, nuclei basal; intestines; absorption, secretion

4. stratified squamous - many layers, flat top; skin, esophagus; protection

5. pseudostratified columnar - nuclei at different heights; trachea; mucus movement

6. transitional - shape-shifting surface cells; bladder; stretch & recoil

Lining vs glandular epithelium

1. Lining

Sheets of cells, layered; distinct apical/ basal surfaces; skin, intestinal lining blood vessels; protection, absorption, diffusion

2. Glandular

Secretory cells, ducts or clusters; often specialized secretory surfaces; goblet cells, sweat glands, pancreas; secretion f enzymes, hormones, mucus

Endocrine vs exocrine glands

1. Endocrine glands

ductless, vascular; hormones directly into bloodstream; systemic (whole body); pituitary, thyroid, adrenal islets

2. Exocrine glands

ducts present; enzymes, mucus, sweat directly to surfaces; local (specific site); sweat, salvairy, pancreas (exocrine), mammary

Components of connective tissue & function

1. fibroblasts - prodcues fibers and matrix

2. macrophages - phagocytosis, defense

3. mast cells - release histamine, inflammation

4. adipocytes - fat storage, insulation

5. leukocytes - immune protection

6. collagen fibers - strength, tensile support

7. elastic fibers - flexibility, recoil

8. reticular fibers - supportive framework

9. ground substance - medium for exchange, cushioning

Types of connective tissure ( 6)

1. Loose connective tissue - areolar( surrounds organs), adipose, reticular; support cushioning fat storage; few fibers & much ground substance

2. Dense connective tissue - regular (resists pulling forces), irregular, elastic; strength, flexibility; packed collagen fibers, little ground substance

3. Cartilage - hyaline, elastic, fibrocartilage; support, flexibility, shock absorption;

4. Bone - compact, spongy’ support, protection, mineral storage

5. Blood - RBCs, WBCs, platelets; transport, defense, clotting

6. Lymph - lymph fluid; fluid balance, immunity

Bone vs. Cartilage function and histological

1. Cartilage

Function - support other tissues, provide smooth surface, serve as model,provide connections

Types - hyaline type collagen; elastic flexible; fibrocartilage tollagen

Cells - contain chandroblasts which secrete the matrix and mature chondrocytes that reside in small places called lacunae

2. Bone

Function- provide rigid mechanical support, protects organs, hematopoeisis

Cells - osteoblasts synthesize and secrete unmineralized bone matrix;

Osteocytes maintain bore tissue (nature cells); osteoclasts break down and

Reabsorb bone matrix to aid din remodeling

Osteoblasts form compact bone, osteocytes connect to one another through canaliculi, spongy bone houses bone marrow

List the histological features of muscle tissue

1. Skeletal

Long cylindrical unbranched, multinucleated, highly visible dark and light sarcoma bands, surrounded by endomysium, perimysium & epimysium

2. Cardiac

Short branches y shape, single centrally located nucleus per cell, intercalated discs contain gap junctions for electrical communication and desmosomes, present stations, not prominent

3. Smooth

Small, spindle shaped cells with tapered ends, single centrally located nucleus that wrinkles when cell contracts, no striating, action filaments only, dark cytoplasmic structures anchor actin filaments