1 Histology  Study of Tissues  Epithelial Tissue  Connective Tissue  Nervous and Muscular Tissue  Intercellular Junctions, Glands and Membranes  Tissue Growth, Development, Death and Repair

2 The Study of Tissues  200 Different cell types  Four primary tissue classes epithelial tissue connective tissue muscular tissue nervous tissue  Histology (microscopic anatomy) study of tissues organ formation  Organ = structure with discrete boundaries composed of 2 or more tissue types

3 Features of Tissue Classes  Tissue = similar cells and cell products arose from same region of embryo arose from same region of embryo  Differences between tissue classes types and functions of cells types and functions of cells characteristics of matrix (extracellular material) characteristics of matrix (extracellular material) fibrous proteinsfibrous proteins ground substanceground substance clear gels (ECF, tissue fluid, interstitial fluid, tissue gel) clear gels (ECF, tissue fluid, interstitial fluid, tissue gel) rubbery or stony in cartilage or bone rubbery or stony in cartilage or bone space occupied by cells versus matrix space occupied by cells versus matrix connective tissue cells are widely separatedconnective tissue cells are widely separated little matrix between epithelial and muscle cellslittle matrix between epithelial and muscle cells

4 Tissue Techniques and Sectioning  Preparation of histological specimens fixative prevents decay (formalin) fixative prevents decay (formalin) sliced into thin sections 1 or 2 cells thick sliced into thin sections 1 or 2 cells thick mounted on slides and colored with histological stain mounted on slides and colored with histological stain stains bind to different cellular componentsstains bind to different cellular components  Sectioning reduces 3-dimensional structure to 2-dimensional slice

5 Sectioning Solid Objects  Sectioning a cell with a centrally located nucleus  Some slices miss the cell nucleus  In some the nucleus is smaller

6 Sectioning Hollow Structures  Cross section of blood vessel, gut, or other tubular organ.  Longitudinal section of a sweat gland. Notice what a single slice could look like.

7 Types of Tissue Sections  Longitudinal section tissue cut along longest direction of organ  Cross section tissue cut perpendicular to length of organ  Oblique section tissue cut at angle between cross and longitudinal section

8 Epithelial Tissue  Layers of closely adhering cells  Flat sheet with upper surface exposed to the environment or an internal body cavity  No blood vessels underlying connective tissue supplies oxygen underlying connective tissue supplies oxygen  Rests on basement membrane thin layer of collagen and adhesive proteins thin layer of collagen and adhesive proteins anchors epithelium to connective tissue anchors epithelium to connective tissue

9 Simple Versus Stratified Epithelia  Simple epithelium contains one layer of cells named by shape of cells Stratified epithelium – contains more than one layer – named by shape of apical cells

10 Simple Squamous Epithelium  Single row of flat cells  Permits diffusion of substances  Secretes serous fluid  Alveoli, glomeruli, endothelium, and serosa

11 Simple Cuboidal Epithelium  Single row cube-shaped cells with microvilli  Absorption and secretion, mucus production  Liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules

12 Simple Columnar Epithelium  Single row tall, narrow cells oval nuclei in basal half of cell  Absorption and secretion; mucus secretion  Lining of GI tract, uterus, kidney and uterine tubes

13 Pseudostratified Epithelium  Single row of cells some not reaching free surface nuclei give layer stratified look  Secretes and propels respiratory mucus

14 Stratified Epithelia  More than one layer of cells  Named for shape of surface cells exception is transitional epithelium exception is transitional epithelium  Deepest cells on basement membrane  Variations keratinized epithelium has surface layer of dead cells keratinized epithelium has surface layer of dead cells nonkeratinized epithelium lacks the layer of dead cells nonkeratinized epithelium lacks the layer of dead cells

15 Keratinized Stratified Squamous  Multilayered epithelium covered with dead squamous cells, packed with keratin epidermal layer of skin  Retards water loss and barrier to organisms

16 Nonkeratinized Stratified Squamous  Multilayered surface epithelium forming moist, slippery layer  Tongue, oral mucosa, esophagus and vagina

17 Stratified Cuboidal Epithelium  Two or more cell layers; surface cells square  Secretes sweat; produces sperm and hormones  Sweat gland ducts; ovarian follicles and seminiferous tubules

18 Transitional Epithelium  Multilayered epithelium surface cells that change from round to flat when stretched allows for filling of urinary tract ureter and bladder

19 Connective Tissue  Widely spaced cells separated by fibers and ground substance  Most abundant and variable tissue type  Functions connects organs connects organs gives support and protection (physical and immune) gives support and protection (physical and immune) stores energy and produces heat stores energy and produces heat movement and transport of materials movement and transport of materials

20 Cells of Connective Tissue  Fibroblasts produce fibers and ground substance  Macrophages phagocytize foreign material and activate immune system arise from monocytes (WBCs) arise from monocytes (WBCs)  Neutrophils wander in search of bacteria  Plasma cells synthesize antibodies arise from WBCs arise from WBCs  Mast cells secrete heparin inhibits clotting heparin inhibits clotting histamine that dilates blood vessels histamine that dilates blood vessels  Adipocytes store triglycerides

21 Fibers of Connective Tissue  Collagen fibers (white fibers) tough, stretch resistant, yet flexible tough, stretch resistant, yet flexible tendons, ligaments and deep layer of the skin tendons, ligaments and deep layer of the skin  Reticular fibers thin, collagen fibers coated with glycoprotein thin, collagen fibers coated with glycoprotein framework in spleen, lymph nodes, marrow framework in spleen, lymph nodes, marrow  Elastic fibers (yellow fibers) thin branching fibers of elastin protein thin branching fibers of elastin protein stretch and recoil like rubberband (elasticity) stretch and recoil like rubberband (elasticity) skin, lungs and arteries stretch and recoil skin, lungs and arteries stretch and recoil

22 Connective Tissue Ground Substance  Gelatinous material between cells absorbs compressive forces absorbs compressive forces  Consists of 3 classes of large molecules glycosaminoglycans – chondroitin sulfate glycosaminoglycans – chondroitin sulfate disaccharides that attract sodium and hold waterdisaccharides that attract sodium and hold water role in regulating water and electrolyte balancerole in regulating water and electrolyte balance Proteoglycan (bottlebrush-shaped molecule) Proteoglycan (bottlebrush-shaped molecule) create bonds with cells or extracellular macromoleculescreate bonds with cells or extracellular macromolecules adhesive glycoproteins adhesive glycoproteins protein-carbohydrate complexes bind cell membrane to collagen outside the cellsprotein-carbohydrate complexes bind cell membrane to collagen outside the cells

23 Fibrous Connective Tissue Types  Loose connective tissue gel-like ground substance between cells gel-like ground substance between cells types types areolarareolar reticularreticular adiposeadipose  Dense connective tissue fibers fill spaces between cells fibers fill spaces between cells types vary in fiber orientation types vary in fiber orientation dense regular connective tissuedense regular connective tissue dense irregular connective tissuedense irregular connective tissue

24 Areolar Tissue  Loose arrangement of fibers and cells in abundant ground substance  Underlies all epithelia, between muscles, passageways for nerves and blood vessels

25 Reticular Tissue  Loose network of reticular fibers and cells  Forms supportive stroma (framework) for lymphatic organs  Found in lymph nodes, spleen, thymus and bone marrow

26 Adipose Tissue  Empty-looking cells with thin margins; nucleus pressed against cell membrane  Energy storage, insulation, cushioning subcutaneous fat and organ packing brown fat (hibernating animals) produces heat

27 Dense Regular Connective Tissue  Densely, packed, parallel collagen fibers compressed fibroblast nuclei  Tendons and ligaments hold bones together and attach muscles to bones

28 Dense Irregular Connective Tissue  Densely packed, randomly arranged, collagen fibers and few visible cells withstands stresses applied in different directions deeper layer of skin; capsules around organs

29 Cartilage  Supportive connective tissue with rubbery matrix  Chondroblasts produce matrix called chondrocytes once surrounded called chondrocytes once surrounded  No blood vessels diffusion brings nutrients and removes wastes diffusion brings nutrients and removes wastes heals slowly heals slowly  Types of cartilage vary with fiber types hyaline, fibrocartilage and elastic cartilage hyaline, fibrocartilage and elastic cartilage

30 Hyaline Cartilage  Rubbery matrix; dispersed collagen fibers; clustered chondrocytes in lacunae supports airway, eases joint movements  Ends of bones at movable joints; sternal ends of ribs; supportive material in larynx, trachea, bronchi and fetal skeleton

31 Elastic Cartilage  Hyaline cartilage with elastic fibers  Provides flexible, elastic support external ear and epiglottis

32 Fibrocartilage  Hyaline cartilage with extensive collagen fibers (never has perichondrium)  Resists compression and absorbs shock pubic symphysis, meniscus and intervertebral discs

33 Bone  Spongy bone - spongy in appearance delicate struts of bone delicate struts of bone covered by compact bone covered by compact bone found in heads of long bones found in heads of long bones  Compact bone - solid in appearance more complex arrangement more complex arrangement cells and matrix surround vertically oriented blood vessels in long bones cells and matrix surround vertically oriented blood vessels in long bones

34 Bone Tissue (compact bone)  Calcified matrix in lamellae around central canal  Osteocytes in lacunae between lamellae  Skeletal support; leverage for muscles; mineral storage

35 Blood  Variety of cells and cell fragments; some with nuclei and some without  Nonnucleated pale pink cells or nucleated white blood cells  Found in heart and blood vessels

36 Nerve Tissue  Large cells with long cell processes surrounded by smaller glial cells lacking processes  Internal communication between cells in brain, spinal cord, nerves and ganglia

37 Muscle Tissue  Elongated cells stimulated to contract  Exert physical force on other tissues move limbs move limbs push blood through a vessel push blood through a vessel expel urine expel urine  Source of body heat  3 histological types of muscle skeletal, cardiac and smooth skeletal, cardiac and smooth

38 Skeletal Muscle  Long, cylindrical, unbranched cells with striations and multiple peripheral nuclei movement, facial expression, posture, breathing, speech, swallowing and excretion

39 Cardiac Muscle  Short branched cells with striations and intercalated discs one central nuclei per cell  Pumping of blood by cardiac (heart) muscle

40 Smooth Muscle  Short fusiform cells; nonstriated with only one central nucleus sheets of muscle in viscera; iris; hair follicles and sphincters swallowing, GI tract functions, labor contractions, control of airflow, erection of hairs and control of pupil

41 Intercellular Junctions  All cells (except blood) anchored to each other or their matrix by intercellular junctions

42 Tight Junctions  Encircle the cell joining it to surrounding cells zipperlike complementary grooves and ridges zipperlike complementary grooves and ridges  Prevents passage between cells GI and urinary tracts GI and urinary tracts

43 Desmosomes  Patch between cells holding them together cells spanned by filaments terminating on protein plaque cells spanned by filaments terminating on protein plaque cytoplasmic intermediate filaments also attach to plaquecytoplasmic intermediate filaments also attach to plaque  Uterus, heart and epidermis

44 Gap Junctions  Ring of transmembrane proteins form a water-filled channel small solutes pass directly from cell to cell small solutes pass directly from cell to cell in embryos, cardiac and smooth muscle in embryos, cardiac and smooth muscle

45 Endocrine and Exocrine Glands  Secrete substances composed of epithelial tissue composed of epithelial tissue  Exocrine glands connect to surface with a duct (epithelial tube)  Endocrine glands secrete (hormones) directly into bloodstream  Mixed organs do both liver, gonads, pancreas liver, gonads, pancreas  Unicellular glands – endo or exocrine goblet or intrinsic cells of stomach wall goblet or intrinsic cells of stomach wall

46 Exocrine Gland Structure  Stroma = capsule and septa divide gland into lobes and lobules  Parenchyma = cells that secrete  Acinus = cluster of cells surrounding the duct draining those cells

47 Types of Exocrine Glands  Simple glands - unbranched duct  Compound glands - branched duct  Shape of gland acinar - secretory cells form dilated sac tubuloacinar - both tube and sacs

48 Types of Secretions  Serous glands produce thin, watery secretions produce thin, watery secretions sweat, milk, tears and digestive juicessweat, milk, tears and digestive juices  Mucous glands produce mucin that absorbs water to form a sticky secretion called mucus produce mucin that absorbs water to form a sticky secretion called mucus  Mixed glands contain both cell types  Cytogenic glands release whole cells sperm and egg cells sperm and egg cells

49 Holocrine Gland  Secretory cells disintegrate to deliver their accumulated product oil-producing glands of the scalp

50 Merocrine and Apocrine Secretion  Merocrine glands release their product by exocytosis tears, gastric glands, pancreas, etc.  Apocrine glands are merocrine glands with confusing appearance (apical cytoplasm not lost) mammary and armpit sweat glands

51 Mucous Membranes  Epithelium, lamina propria and muscularis mucosae  Lines passageways that open to the exterior: reproductive, respiratory, urinary and digestive Mucous (movement of cilia) trap and remove foreign particles and bacteria from internal body surfaces

52 Membrane Types  Cutaneous membrane = skin stratified squamous epithelium over connective tissue stratified squamous epithelium over connective tissue relatively dry layer serves protective function relatively dry layer serves protective function  Synovial membrane lines joint cavities connective tissue layer only, secretes synovial fluid connective tissue layer only, secretes synovial fluid  Serous membrane (serosa) –internal membrane simple squamous epithelium over areolar tissue, produces serous fluid simple squamous epithelium over areolar tissue, produces serous fluid covers organs and lines walls of body cavities covers organs and lines walls of body cavities

53 Tissue Growth  Hyperplasia = tissue growth through cell multiplication  Hypertrophy = enlargement of preexisting cells muscle grow through exercise muscle grow through exercise  Neoplasia = growth of a tumor (benign or malignant) through growth of abnormal tissue

54 Tissue Repair  Regeneration replacement of damaged cells with original cells replacement of damaged cells with original cells skin injuries and liver regenerate skin injuries and liver regenerate  Fibrosis replacement of damaged cells with scar tissue replacement of damaged cells with scar tissue function is not restoredfunction is not restored healing muscle injuries, scarring of lung tissue in TB or healing of severe cuts and burns of the skin healing muscle injuries, scarring of lung tissue in TB or healing of severe cuts and burns of the skin keloid is healing with excessive fibrosis (raised shiny scars) keloid is healing with excessive fibrosis (raised shiny scars)

55 Wound Healing of a Laceration  Damaged vessels leak blood  Damaged cells and mast cells leak histamine dilates blood vessels increases blood flow increases capillary permeability  Plasma carries antibodies, clotting factors and WBCs into wound

56 Wound Healing of a Laceration  Clot forms  Scab forms on surface  Macrophages start to clean up debris

57 Wound Healing of a Laceration  New capillaries grow into wound  Fibroblasts deposit new collagen to replace old material  Fibroblastic phase begins in 3-4 days and lasts up to 2 weeks

58 Wound Healing of a Laceration  Epithelial cells multiply and spread beneath scab  Scab falls off  Epithelium thickens  Connective tissue forms only scar tissue (fibrosis)  Remodeling phase may last 2 years