Histology Lecture Notes: Human Tissues PDF

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 other...

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!!! HISTOLOGY, Continued Chapter 5 Connective tissue, nervous tissue,& muscle tissue Connective Tissue Most abundant, widely distributed, and histologically variable type of tissue Cells occupy less space than matrix Most cells are not in direct contact with each other Highly variable vascularity Loose connective tissues have many blood vessels Cartilage has no blood vessels Connective Tissue Main types 1.Fibrous 2.Adipose 3.Supportive 4.Fluid Connective Tissue Most abundant, widely distributed, and histologically variable type of tissue Functions of Connective Tissue Bind organs to each other (e.g., fat holds kidneys) Support (e.g., cartilage supporting ears) Protection (Structural and immunological) Movement (e.g., bones lever system) Storage (e.g., fat for energy, calcium in bone) Heat production (metabolism of brown fat) Transport or substances (nutrients, waste, hormones, blood cells) Fibrous Connective Tissue Cell types: Fibroblast: produce fibers and matrix gel (ground substance) Leukocytes (WBCs): attack and react against bacteria Macrophages: phagocytize foreign material, activate immune system Plasma (B) cells: make antibodies Mast cells: secrete heparin (inhibit clotting) and histamine (allergic reaction, vasodilation) Fibrous Connective Tissue Fiber types Collagenous (white fibers) Tough, resist stretching E.g., found in tendons, ligaments, dermis Reticular Thin, sponge-like, coated with glycoprotein Framework for some organs (e.g., spleen, lymph nodes) Part of basement membrane (epithelial) Elastic Elastin and fibrillin Ability for tissues/organs to spring back after stretched Fibrous Connective Tissue Loose connective tissue Large space between cells 1. Areolar Loosely organized fibers Beneath epithelial layers Contains blood vessels 2. Reticular Reticular fibers and fibroblasts Blood between fibers (like bloody sponge) Fibrous Connective Tissue Dense connective tissue Fibers occupy more space than cells & matrix Tightly packed 1. Dense regular Collagen fibers + fibroblasts Collagen fibers tightly packed Fibers parallel (predictable muscle movement/stress) 2. Dense irregular Collagen fibers – random directions Adipose Tissue Adipocytes Store fat (energy reservoir) Not stagnant  constant turnover (equilibrium) 2 types of fat 1. White fat Most abundant Insulation, cushions organs 2. Brown fat Fetuses, infants, children Shoulders, upper back Enzymes and blood vessels Generates heat  Release ALL energy as heat Diagram: white fat Cartilage Firm CT, flexible matrix Shape and support Chondroblasts Produce cartilage Secrete matrix until surrounded  Become chondrocytes Avascular Cartilage 3 Types 1. Hyaline Hyaline cartilage Fineness of collagen fibers  Clear, glassy Eases joint movement, holds airway open, moves vocal cords, growth of juvenile long bones 2. Elastic 3. Fibrocartilage Cartilage 3 Types 1. Hyaline Hyaline cartilage 2. Elastic Contain elastic fibers Provides flexible, elastic support Elastic cartilage Locations: external ear and epiglottis 3. Fibrocartilage Cartilage 3 Types 1. Hyaline Hyaline cartilage 2. Elastic 3. Fibrocartilage Large, course bundles of collagen Elastic cartilage Resists compression and absorbs shock Locations: pubic symphysis, menisci, and intervertebral discs Fibrocartilage Bone Calcified 1. Spongy Heads of long bones Middle of flat bones 2. Compact Dense, no visible spaces External surfaces (covers spongy bone when present) Blood Transport cells and matter Fluid CT More ground substance/matrix than cells  blood plasma Produced by tissues of bone marrow Formed elements Cell components of blood plasma 1. Erythrocytes (RBCs) 2. Leukocytes (WBCs) Nervous Tissue Communication Electrical signaling Chemical signaling Neurons Detect stimuli Transmit information Neuroglial cells Support cells for neurons “housekeepers” of nervous system Neuroglial Cells Microglia Immune response Hyperactive in Alzheimer’s disease Astrocytes Peripheral Maintain environment Central Nervous System Nervous System Oligodendrocytes Axon support – myelin sheaths (CNS) Schwann cells Myelinate axons (PNS) Ependymal cells Muscle Tissue Muscle Fiber = cell (in muscle) Contract when stimulated Exert force on tissues, organs, fluids Movement Digestion Breathing Circulation 1. Skeletal 2. Smooth Skeletal Muscle Made of muscle fibers—long thin cells Most skeletal muscles attach to bone Contains multiple nuclei adjacent to plasma membrane Striations—alternating dark and light bands Voluntary—conscious control over skeletal muscles Cardiac Muscle Limited to the heart wall Cardiomyocytes are short and branched with one centrally located nucleus; muscle, short, cells of the heart Intercalated discs join cardiomyocytes end to end Gap junctions Striated and involuntary (not under conscious control) Smooth Muscle Made of short, fusiform- shaped cells Cells have one central nucleus, no striations Involuntary function Gap junctions Most is visceral muscle— making up parts of walls of hollow organs Membranes Faces the outside environment & line cavities and organs & Cutaneous membrane: skin Internal membranes 1. Mucous membrane Line passage to external environment Epithelium, areolar CT, smooth muscle Next: Integumentary System & Bones