tissue

Microscopic structure and composition of tissues

Study of both healthy and diseased tissue

A person who specialized in the study of both healthy and diseased tissue

• sheets of cells that cover all of the internal and external surfaces of the body and line all of the bodys cavities
• *Digestive tract, urinary tract and blood vessels*
• protect underlying tissues and may act to filter biochemical substances
• may absorb, secrete or excrete biochemical substances
• may play a role in the reception of sensory input

• Each epithelial cell has an apical surface and a basal surface *apical surface faces the lumen or outside of the organ, basal surface faces the basal lamina and blood vessels*
• Lateral surfaces are connected to neighboring cells by junctional complexes
• Epithelial cells are avascular
• Most epithelial cells are innervated

• Tight juntions
• Desmosomes
• Gap junctions

• Formed by the fusion of the outermost layers of the plasma membranes of adjoining cells
• Found in tissues which there can be no leaks (urinary bladder, digestive tract)

• Tubular channel proteins (connexons) that extend from the cytoplasm of one cell to the cytoplasm of another
• Allow the exchange and passage of ions and nutrients
• Found in intestinal epithelial cells, the heart and smooth muscle tissue

• Meshwork of fibers that cements the epithelial cell to the underlying connective tissue
• Also called the basal lamina
• Varies in thickness
• Helps prevent the cell from being torn off by intraluminal pressures
• Acts as a partial barrier between the epithelial cell and the underlying connective tissue

• Surfaces of epithelial cells vary depending on where they are located and what role they play in the function of the tissue
• Smooth
• microvilli (brush border)
• cillia
• keratin

• number of layers of cells *simple or stratified*
• shape of the cells *squamous, cuboidal and columnar*
• presence of surface specializations*cillia, keratin, etc.*

• fragile and thin
• found in the lining surfaces involved in the passage of either gas or liquid *lung, kidney*
• flat and smooth

• single layer of cube-shaped cells
• round, dark-staining nuclei aligned in a single row
• occurs in areas of the body where secretion and absorption take place*ovaries, thyroid, lining of ducts of the liver, pancreas, kidney, and salivary glands*

• Elongated and closely packed together
• nuclei aligned in a row at the base of the cell near the basement membrane
• found in may excretory ducts as well as the digestive tract

• Multilayered
• occurs in areas of the body subject to mechanical and chemical stresses *lining of the mouth, esophagus, vagina and rectum*
• protects the underlying tissues

• usually two layers of cuboidal cells
• found primarily along large excretory ducts*sweat glands, mammary glands,salivary glands*
• protects underlying tissues

• sound only in select parts of the respiratory, digestive, reproductive systems and along some excretory ducts
• functions in secretion and protection

• cell nuclei are found at different levels across the length of the tissue
• some cells do not reach the luminal surface
• found in respiratory tract and in protions of the male reproductive tract
• *look like multi layered, they are not, still one layer*

• stratified epithelium with a basal layer of cuboidal or columnar cells and a superficial layer of cuboidal or squamous cells
• found in areas of the body required to expand and contract as part of their normal function*bladder, urethra,ureters, calyxes of the kidney*

• groups of cells that manufacture and discharge a secretion
• classification of glands is by
• 1- presence or absence of ducts,
• 2- number of cells that compose them, 3-shape of the secreting ducts,
• 4-complexity of the glandular structure,
• 5-type of secretion they produce
• 6-manner in which the secretion is stored and discharged

• glands that do NOT have ducts or tubules and whose secretions are distributed throughout the body
• produce and secrete hormones into the bloodstream or lymphatic system
• part of a complex biochemical network know as the endocrine system

• discharge secretions via ducts directly into local areas (except for the goblet cell)
• unicellular or multicellular

• unicellular exocrine gland
• ductless and composed of modified columnar epithelial cell
• found among columnar cells of the respiratory and digestive tracts and the conjunctiva of the eye
• secretes mucin - thick, sticky mixture of glycoprotiens and proteoglycans = mucus
• mucus functions in 2 ways, protect the apical surface of the epithelial layer and entrapment of microorganisms and foreign body

• composed of a secretory unit and a duct
• secretory unit is usually surrounded by connective tussue rich in blood vessels and nerve fibers
• may be surrounded by myoepithelial cells that assist with the discharge of secretions into the glandular duct

• ducts
• -simple:the main duct in unbranched
• -compound:the main duct is branched
• shape of secretory portions
• -tubular:secretory cells form a long channel of even width
• -alveolar or acinar:secretory init forms a rounded sac
• -Tubuloalveolar or tubuloacinar:secretory units posses both tubular and alveolar qualities

• merocrine glands package their secretions and release them via exocytosis as they are manufactured (the cells remain intact, only secrete at the top) pancreas, sweat glands, and salivary glands
• Apocrine glands store their secretions and then release the top part of the cell into the duct system(mammary tissue)
• Holocrine glands store their secretions and then release the entire contents of the cell, the entire cell is destroyed -move from the basal layer up (sebaceous glands)

• serous secretions
• -watery
• -contain a high concentration on enzymes
• mucous secretions
• -thich, viscous
• -compound of glycoproteins
• mixed exocrine glands contain both mucous and serous components

• forms metabolic and structural connections between other tissues
• forms a protective sheath around organs and helps insulate the body
• acts as a reserve for energy
• provides the frame that supports the body
• composes the medium that transports substances from one region of the body to another
• plays a role in the healing process and in the control of invading microorganisms

• extracellular matrix = extracellular fibers and ground substance
• cells

• medium through which cells exchange nutrients and wast with the bloodstream
• amorphous, homogenous material
• ranges in texture from a liquid or gel to a calcified solid
• acts to protect the more delicate cells in envelopes
• serves as an affective obstacle for invading microorganisms

• they line the walls and cover the organs
• the portion that lines the cavity wall = parietal
• the portion that covers the outer surface of the organs = visceral

its a transudate = able to pass through into the narrow spaces between the serosal layers

• thorax = pleural fluid
• abdomen = peritoneal fluid
• heart = pericardial fluid

when cells, protein and other solid material mix with serous fluid, it becomes denser than a transudate

large amount of fluid enters a body cavity

effusion in the peritoneal space in the abdomenopelvic cavity

• strong, thick strands of collagen
• organized into bundles of long, PARALLEL fibrils composed of bundled microfibrils
• variable density and arrangement of fibers
• found in tendons and ligaments

• thin, delicate, branched network of collagen
• provide support for highly cellular organs(endocrine glands, lymph nodes, spleen, bone marrow and liver)
• also found around blood vessels, nerves, muscle fibers and capillaries

• branched networks composed primarily of the protein elastin
• composed of coiled bundles of microfibrils
• occur in tissue commonly subjected to stretching (vocal cords, lungs, skin, walls of blood vessels)

• Fixed cells = involved in the production and maintenance of the matrix (fibroblasts, chondroblasts, osteoblasts,adipocytes and reticular cells)
• Transient cells = involved in the repair and protection of tissue (leukocytes, mast cells, macrophages)

• 3 common types are...
• leukocyes
• mast cells
• macrophages

• leukocytes: found in blood and move into connective tissue in large numbers
• although larger than RBC, they squeeze through the walls of tiny blood vessels to enter the tissue - diapediesis

• Mast cells: oval cells that are easily identified by the large dark-staining granules stored in the cytoplasm
• these granules contain histamine and heparin

• Macrophages: massive, irregular shaped phagocytizing scavangers
• engulf microbes, dead cells and debris that are subsequently digested in the macrophages lysosomes
• drawn to sites of infection and inflammation

liver macrophages

brain macrophages

connective tissue macrophages

• Areolar
• Adipose
• Reticular

• Dense regular
• Dense irregular
• Elastic

• loose connective tissue
• fibers and cells suspended in a thick, translucent ground substance
• predominent cells is the fibroblast
• fibroblast manufactures the elastic, reticular and collagenous fibers
• surrounds every organ; forms the SQ layer that connects skin to muscle; envelopes blood vessels, nerves and lymph nodes; present in all MM

• loose connective tissue
• areolar tissue in which adipocytes predominate
• highly vascular
• acts as an energy storehouse and a thermal insulator

• loose connective tissue
• network of thin reticular fibers and mainly fibroblasts suspended in a supportive ground substance
• forms the stroma (framework of several organs)

• composed of tightly packed, paralled collagen fibers
• relitively avascular
• makes up tendons and ligaments
• can be found in fascial sheets that cover muscle

• Composed primarily of collagen fibers arranged in thick bundles
• fibers are interwoven to form a single sheet
• found in the dermis of the skin and in the fibrous coverings of many organs
• forms the tough capsule of joints

• primarily composed of elastic fibers
• fibers may be arranged paralled or in interwoven patterns with fibroblasts and collagenous fibers interspersed
• found in spaces between vertebrae and in areas of the body that require stretching (walls of arteries, stomach, bronchi and bladder)

• Cartilage - hyaline, elastic, fibrocartilage
• Bone
• Blood

• found in joints and in the ear, nose and vocal cords
• forms a framework on which bone is formed
• Cells: chondrocytes live in the hollowed out pockets in the matrix called lacunae
• Matrix: ground substance is a gel made up of chondoitin sulfate, hyaluronic acid and chondronectin
• collagen fibers are most commonly found in the matrix, but elastic fibers are also present in varying amounts

• most common type of cartilage found in the body
• compsed of closely packed collagen
• found in joints at the ends of long bones, growth plates of long bones, tracheal rings and connections of the ribs to the sternum
• composes most of the embryonic skeleton
• enclosed within a perichondriium

• contains elastic fibers in dense branching bundles
• flexible and can withstand repeated bending
• found in the epiglottis of the larynx and in the pinnea of the ears in animals

• usually found merged with hyaline cartilage and dense connective tissue
• contains thick bundles of collagen fibers with fewer chondrocytes than hyaline cartilage
• lacks a perichondrium; found in spaces between vertebrae of the spine, between bones in the pelvic girdle and int he knee joint

• matrix is a combination of organic collagen fibers and inorganic calcium salts
• well vascularized
• haversian canal contains both a vascular and a nerve supply
• canaliculi are channels within the matrix that supports passage of blood vessels into deeper portions of tissue
• osteoblasts manufacture the fibers that are part of the matirx
• Lacunae and canaliculi are created as the osteoblasts manufacture the bony matrix
• osteocytes reside in the lacunae
• cellular extensions pass through the cabaliculi

• Matix = ground substance = plasma, fibrous component = protein
• Cells = erythrocytes, leukocytes, thrombocytes

• line organs with connections to the outside environment ( mouth, intestines, nasal passages)
• usually composed of either stratified squamous or simple columnar epithelium covering a layer of loose connective tissue
• submucosa is the connective tissue layer that connects the mucosa to underlying structures
• may contain goblet cells or multicellular glands; can produce large quantites of mucus
• some mucosae also can absorb (the epithelial layer in the intestines)

• line walls and cover organs of the body cavities (thorax and abdomen)
• consists of a continuous sheet doubled over on itself to form 2 layers)
• the portion of the membrane that lines the cavity wall is called the PARIETAL layer
• the portion of the membrane that covers the outer surface of organs is called the VISCERAL layer
• in abdominopelivic cavity, visceral layers of serosa merge to form mesenteries

• also called integument (skin)
• composed of an outer keratinized stratified squamous epithelium or epidermis
• epidermis is attatched to an underlying layer of dense irregular connective tissue called the dermis
• dermis contains collagenous, reticular and elastic fibers which enable skin to be both strong and elastic

• line the cavities of joints
• composed of loose connective tissue and adipose tissue covered by a layer of collagen fibers and fibroblasts
• manufacture the synovial fluid that fills the joint spaces

• composed of actin and myosin fibers
• 3 types of muscle tissue; skeletal, smooth, cardiac

• large cells that contain hundreds of nuclei and mitochondria
• usually controlled through conscious efforts (VOLUNTARY MUSCLE)
• skeletal muscle cells are striated
• skeletal muscle cells are bundles of fibers held together by loose connective tissue
• the collagen fibers that surround the cells merge with the collagen fibers in tendons

• composed of small, spindle - shaped cells that lack striations
• muscle contractions cannot be consciously controlled (NONSTRIATED, INVOLUNTARY MUSCLE)
• found in walls of hollow organs, in endocrine glands and alongh the respiratory tract
• responsible for peristalsis in the GI tract, constrictions of blood vessels and emptying the urinary bladder

• found only in the heart
• contains specialized pacemaker cells that supply the signal for the heart to contract at regular intervals
• entirely INVOLUNTARY AND STRIATED
• cardiac muscle cells connected to one another by intercalated disks (intercellular junctions)

• found in the brain, spinal cord and peripheral nerves
• composed of 2 general cell types; neurons and supporting neuroglial cells

longest cell in the body with three primary parts, 1 perikaryon=cell body containing the nucleus, 2 dendrites=short cytoplasmic extensions that receive nerve impulses, 3 axon=long, single extensions that conducts impulses away from the cell body

support the neurons

• simple squamous
• simple cuboidal
• simple columnar
• stratified squamous
• stratified cuboidal
• stratified columnar
• transitional
• pseudostratified

• Connective Tissue Proper: loose connective tisse = areolar, adipose and reticular tissue
• Dense Connective tissue: Dense regular, dense irregular and elastic
• Specialized Connective Tissue: cartilage = hyaline, elastic and fibrocartilage
• Bone: compact and cancellous
• Blood:
• Muscle tissue: skeletal(striated voluntary), cardiac (striated, involuntary), smooth ( nonstriated, involuntary)

• Inflammation - the initial response to injuries in which the goal is to limit further damage and eliminate any harmful agents
• Repair - involves organization of granulation tissue and regeneration of lost tissue or formation of scar tissue

• nonspecific reaction to injurty or disease
• steps: 1 vasodilation, 2 swelling, 3 clot formation,4 phagocytosis, 5 capillaries return to normal size, blood flow and fluid leakage into the affected area abate

• tissues that form beneath the overlying flood clot or scabs
• compsed of a layer of collagen fibers infiltrated with capillaries (that have branched off existing capillaries in deeper layers of damaged tissue)
• granulation tissue is slowly replaced by fibrous scar tissue

• First Intention: egdes of wound held in close apposition, skin forms a primary union without formation of granulation tissue or significant scarring
• Second Intention: edges of wound seperated from eachother, granulation tissue forms to close the gap; scarring results
• Third Intention: contaminated would left open until contamination is reduced and inflammation subsides; later closed by first intention; also called delayed primary closure