Chapter 5 Tissues – Epithelial, Connective, Muscle, Nervous, Membranes

HISTOLOGY: THE HUMAN TISSUES Chapter 5 Tissues – epithelial, connective, muscle, nervous, membranes Objectives • Visualize 3D shape from 2D sections • Name the primary classes of adult tissues • Distinguish and visually recognize specific tissue types from others • Relate form to function for all tissue types • Describe types and composition of the body’s membranes Tissue • Human body = ~50 trillion cells • 200 cell types • E.g., RBCs, neuroglial cells, smooth muscle cells, stem cells, cartilage cells, etc. • Same genetics, differing gene expression • Tissue • Similar cells & matrix (interstitial fluid) working together • Each tissue has a specific role in organ • Organs derive functions from tissue • Histology • Microscopic anatomy • Study of tissues and they are arranged into organs Tissue Classes 1. Epithelial 2. Connective 3. Nervous 4. Muscular • Extracellular material (matrix) • Fibrous proteins • ECF, interstitial fluid, tissue fluid, etc. Tissue Classes 1. Epithelial 2. Connective 3. Nervous 4. Muscular • Differ from each other in: • Types and functions of their cells • Characteristics of the matrix (extracellular material) • Relative amount of space occupied by cells and matrix Section Axes: 3D  2D • Longitudinal section —tissue cut on its long axis • Cross section or transverse section— tissue cut perpendicular to long axis of organ • Oblique section— tissue cut at angle Visualize 3D shape from 2D sections Histology • Smear • Tissue rubbed across slide • E.g., blood • Spread • Laid on slide • Slice of tissue • E.g., areolar connective tissue, duodenum section. Epithelial Tissue • Sheet of close cells, 1+ cells thick • One surface exposed to environment or internal space • Body surface, cavities, linings of organs • Functions • Protect deeper tissues • Produce and release secretions (glands; mucus, sweat, enzymes) • Excrete wastes (e.g., CO2, bile) • Absorb chemicals (e.g., small intestine) • Selectively filter (e.g., kidneys, blood) Epithelial Tissue • Cells close together • Avascular • Nourished by underlying connective tissue • High rate of mitosis Epithelial Tissue • Basal membrane • Side of cell facing basement membrane • Apical Surface • Surface facing away • Basement membrane • Collagen, glycoproteins • Anchors to CT • Regulated materials passing • Epithelial growth factors Simple Epithelia • Simple • One layer • Named by shape • Cells touch basement membrane • Squamous, cuboidal, columnar, pseudostratified columnar • Goblet Cells • Wineglass-shaped • Within columnar epithelia • Secrete mucus Simple Squamous Epithelia • Single row of thin & flattened cells • Permits rapid diffusion or transport of substances • Secretes serous fluid • Allows lubricated sliding movement • Locations: alveoli, glomeruli, endothelium, and serosa Simple Squamous Epithelia Simple Cuboidal Epithelia • Single layer of square or round cells • Absorption and secretion, mucus production and movement • Locations: liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules Simple columnar epithelium • Single row of tall, narrow cells • Oval nuclei in basal half of cell • Brush border of microvilli, ciliated in some organs, may possess goblet cells • Tight junctions  Absorption • Secretions: (e.g., enzymes) • Goblet cells  Secrets mucus • Locations: lining of GI tract, kidney, uterus, and uterine tubes Pseudostratified epithelium • Looks multilayered, but all cells touch basement membrane • Not all cells reach the surface • Nuclei at several layers • Has cilia and goblet cells • Secretes and propels mucus • Locations: respiratory tract and portions of male urethra Pseudostratified epithelium Stratified Epithelia • Stratified = >1 layer • Named by shape of apical cells • Squamous • Deepest layer  mitosis • Top layer flakes off (exfoliation, desquamation) • Two kinds 1. Keratinized (skin surface, abrasion resistant) 2. Nonkeratinized (lacks dead surface cells) • Cuboidal • Columnar Keratinized stratified squamous • Multiple cell layers; cells become flat and scaly toward surface • Kerantinocytes: dead compressed cells packed with keratin & coated in glycolipids • Dry, tough & water resistant. • 1) Resists abrasion; 2) retards water loss through skin; 3) resists penetration by pathogenic organisms • Locations: epidermis; palms and Nonkeratinized stratified squamous • Same as keratinized epithelium without surface layer of dead cells • Resists abrasion and penetration of pathogens • Locations: tongue, oral mucosa, esophagus, and vagina Stratified cuboidal epithelium • Two or more cell layers; surface cells square or round • Secretes sweat, produces sperm, produces ovarian hormones • Locations: sweat gland ducts, seminiferous tubules, and ovarian Transitional epithelium (Urothelium) • Multilayered epithelium with surface cells that change from round to flat when stretched • 5-6 cells thick when relaxed  2-3 cells thick when stretched • Allows for filling of urinary tract • Locations: ureter and bladder • Umbrella cells at surface Glands • Secretory epithelial cells • Endocrine • Lose connection to surface: lack ducts • Secrete hormones into the blood system • Exocrine • Contents released thru ducts • Secretes onto body surface (e.g., sweat, milk) or into lumen of organ (e.g., digestive Glands (secretory epithelial cells) 1. Endocrine • E.g., alpha cells  glucagon • E.g., Beta cells  insulin 2. Exocrine • E.g., acinar cells  digestive enzymes Pancreas has both!!!