Chapter 5 TISSUES

HISTOLOGY The science that deals with the study of tissues

PATHOLOGIST Scientist who specializes in laboratory studies of cells and tissues to help physicians make accurate diagnoses

Four basic types of tissues Epithelial covers body surfaces, lines body cavities Connective protects and supports, binds organs together, stores energy Muscle generates force Nervous initiates and transmits impulses

Epithelial tissue Closely packed Arranged in continuous sheets Have a free (superficial) surface, exposed to a body cavity Have a basement membrane No vascular tissue; exchange of materials is by diffusion with connective tissue Have nerve supply High capacity for renewal Functions include; protection, secretion, absorption, excretion, sensory reception, generation of gametes

Covering and lining epithelium Four basic shapes: –Squamous flat –Cuboidal cubes –Columnar Tall cylindrical –Transitional Range in shape from flat to columnar; often change shape due to distention

Arrangement of layers: –Simple single –Stratified Two or more layers –Pseudostratified One layer; but appears to have many

Simple squamous Found where filtration or diffusion are priority Air sacs of lungs; walls of capillaries; covers membranes of body cavities Thin, delicate; easily damaged

Simple cuboidal Functions of secretion and absorption Found in kidney tubules, many excretory ducts of glands

Simple columnar Two forms: Ciliated –Cilia –Upper respiratory tract, uterine tubes (oviducts) Nonciliated –Contains absorptive cells (w/ microvilli) and goblet cells (secrete mucus) –Linings of digestive, respiratory, reproductive

Stratified squamous Superficial cells flat; deep cells vary from cuboidal to columnar Forms outer layer of skin; lines oral cavity, esophagus, vagina, anal canal Keratinized –Contain keratin-tough protein resistant to friction; helps repel bacteria Nonkeratinized –No keratin; remains moist

Stratified cuboidal Function: protection, in some locations; secretion and absorption Sweat glands, mammary glands, salivary glands, pancreas

Stratified columnar Uncommon Functions in protection and secretion Found in male urethra, vas deferens, parts of pharynx

transitional Varies in appearance Looks similar to stratified cuboidal; except superficial cells are large and rounded Urinary bladder Allows organs to stretch w/out rupturing; helps prevent contents from diffusing back into internal environment

Pseudostratified columnar Nuclei of cells are at various depths; all cells are attached to basement membrane in a single layer Commonly have cilia Lines passageways of respiratory system

Pseudostratified

Connective Tissue Bind structures, provide support and protection, serve as frameworks, fill spaces, store fat, produce blood cells, protect against infection, help repair tissue damage

CT general features Cells are farther apart then epithelial cells Consists of 2 basic elements –Cells –Extracellular Matrix consists of: –protein fibers –ground substance »Consists of nonfibrous protein, other molecules, and fluid »Maybe fluid, semifluid, gelatinous, fibrous, calcified Does not occur on free surfaces has nerve supply (exception cartilage) Usually highly vascular (exception cartilage, avascular and tendons, scanty blood supply)

CT cells Each major type of CT cell contains immature cells (-blast) Blasts –have ability to divide; secrete matrix –fibroblasts= loose and dense CT –Chondroblasts= cartilage –Osteoblasts= bone

Cartilage and bone Once matrix is produced fibroblasts change into mature cells (-cyte) Do not divide or form matrix like -blasts –Chondrocytes –Osteocytes

Types of cells in CT Fibroblasts –Large flat spindle shaped w/ branching processes –Found in all CT –Most numerous cell in CT –Migrate thru secreting fibers and ground substance Macrophages –Irregular shape cell w/ short branching projections –Engulf bacteria and cellular debris Plasma cells –Small, either round or irregular –Secrete antibodies –Reside in CT, especially GI tract and mammary glands Mast cells –Abundant alongside blood vessels that supply CT –Produce histamine-dilates sm blood vessels, reaction to injury, infection Adipocytes –Fat cells; found below skin, around organs White blood cells –Not found in significant #’s in normal CT

CT matrix Ground substance plus protein fibers –Ground substance: Contains assortment of large molecules; many are complex combinations of polysaccharides and proteins –Fibers: Strength and support CT 3 types embedded in matrix between cells: –Collagen fibers –Elastic fibers –Reticular fibers

Collagen fibers Strong and resist pulling forces; not stiff- promotes tissue flexibility Occur in bundles lying parallel to each other Consist of protein- collagen Most abundant protein in your body Found in most types of CT (bone, cartilage, tendons, ligaments)

Elastic fibers Smaller in diameter than collagen fibers Branch and join together to form a network Consist of protein (elastin) surrounded by glycoprotein (fibrillin) Strong but can be stretched Plentiful in skin, blood vessel walls, lung tissue

Reticular fibers Consisting of collagen and coating of glycoprotein Provide support in walls of blood vessels and form branching networks around fat cells, nerve fibers, skeletal and smooth muscle cells Produced by fibroblasts, much thinner than collagen fibers Form supporting framework of many soft organs Help form basement membrane

Classification of CT Connective tissue proper: –Loose –Dense Specialized connective tissue: –Cartilage –Bone –Blood –Lymph

Loose CT Areolar CT –Subcutaneous layer –Attaches skin to underlying tissues Adipose tissue –fat Reticular CT –Forms stroma (bed or covering) of certain organs –Helps bind together smooth muscle

Dense CT Dense regular CT –Silvery white and tough –Tendons, most ligaments Dense irregular CT –Occurs in sheets –Dermis, heart valves, perichondrium (membrane surrounding cartilage), periosteum (membrane surrounding bone) Elastic CT –Yellowish color; lung tissue, elastic arteries

Cartilage Hyaline –Bluish-white, shiny –Joints, epiphyseal plates (growth), nose Fibrocartilage –Strongest, lacks perichondrium –Discs between vertebrae Elastic –Maintains shape of certain structures like external ear

Blood and lymph Blood= Liquid matrix Lymph= clear fluid, similar to plasma but w/ much less protein

Bone Organ composed of different CT –Bone or osseous tissue –Periosteum-tough, vascular covering on outside of bone –Red and yellow bone marrow –Endosteum- membrane that lines space w/in bone that stores yellow bone marrow

Basic unit of compact bone Osteon or Haversian system –Composed of: Lamellae –Concentric rings of matrix; mineral salts; collagen fibers Lacunae –Small spaces between lamellae; contains mature bone cells (osteocytes) Canaliculi –Project from lacunae; network of small canals containing osteocytes provide routes for nutrients to reach osteocytes and wastes to leave Central (Haversian) canal –Contains blood vessels and nerves

Cancellous/Spongy bone No osteons Columns of bone called trabeculae –Which contain lamellae; osteocytes; lacunae; canaliculi –Spaces between lamellae filled w/ red bone marrow