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Tissues Chapter 3. Histology. Study of tissues (approximately 220 types!) Tissues: groups of highly specialized cells performing functions that benefit the organism as a whole Cells must be similar in structure & function and come from similar embryonic origin Four Primary tissue types - PowerPoint PPT Presentation
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Tissues
Chapter 3
Histology• Study of tissues (approximately 220
types!)• Tissues: groups of highly specialized
cells performing functions that benefit the organism as a whole– Cells must be similar in structure &
function and come from similar embryonic origin
• Four Primary tissue types– Epithelium (covering)– Connective (support)– Muscle (movement)– Nervous (control)
• Organs contain several tissue types, and arrangement of tissues determines organ’s structure & function
Primary Germ Layers• All tissues & organs of the body
develop from one of three primary germ layers:– Ectoderm (outside)
• Lining, skin, nervous – Endoderm (inside)
• Organs, mucosae & glands, linings of cavitiesand tracts
– Mesoderm (middle)• Connective tissue (i.e. blood, bone) and most muscle tissue
Extracellular Materials• ECF: usually fluid, but can be more
gel-like or calcified (i.e. bone)• ECF provides a medium for:
– Dissolving & mixing solutes– Transporting substances– Carrying out chemical reactions
Epithelial Tissue• a.k.a. epithelium (“epithe” = laid on,
covering)• Lining, covering, and glandular tissue
of the body• Covers all free body surfaces and
contains versatile cells• Nearly all substances that the body
gives off or receives must pass through epithelium
• Functions:– Protection– Filtration– Absorption– Secretion
Characteristics of Epithelium• Cells fit closely together to form continuous
sheets – single or multiple layers (desmosomes & tight junctions); little extracellular materials
• Membranes always have one free (unattached) surface or edge (apical surface) that is exposed to body’s exterior or to the cavity of an internal organ (some have modifications like cilia or microvilli)
• Basal surface (lower) of epithelium rests on a basement membrane – structureless material secreted by both epithelial cells and connective tissue cells that border the epithelium
• Epithelial tissues have no blood supply of their own (avascular) and depend on diffusion from the capillaries in underlying connective tissue for food and oxygen
• Regenerate easily (high mitotic rate)• Have a nerve supply• Derived from all three primary germ layers
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Classification of Epithelium
• Two names: – 1st indicates relative number of cell layers
• Simple (one layer) or stratified (multiple layers) or pseudostratified (looks like multiple layers)
– 2nd indicates the shape of its cells• Squamous (flat)• Cuboidal (cube)• Columnar (shaped like columns)• Transitional (varies)
• Stratified epithelium is named based on cells at the free surface!
• Arrangement reflects location and function
Types of Epithelial Tissue
• Covering & Lining Epithelium– Simple Epithelia
• Simple squamous epithelium• Simple cuboidal epithelium• Simple columnar epithelium• Pseudostratified columnar epithelium
– Stratified Epithelia• Stratified squamous epithelium• Stratified cuboidal epithelium • Stratified columnar epithelium• Transitional epithelium
• Glandular Epithelium
Epithelial Tissue ID Quiz
Tissues you need to be able to identify:
• Simple squamous
• Simple cuboidal• Simple
columnar• Stratified
squamous• Transitional• Pseudostratified
Tissue/ cell parts you need to know:
• Nucleus• Apical (free)
surface• Basal surface• Basement
membrane• Cilia• Goblet cell• Keratin
Simple Squamous Epithelium• Single layer, flat shape
• All cells attached to basement membrane• Fit closely together• Forms membranes where filtration or
exchange of substances by rapid diffusion occurs (absorption, secretion, filtration)
• Ex: air sacs of lungs (O2 & CO2 exchanged), walls of capillaries (nutrients and gases pass between the tissue cells and blood in capillaries), form serous membranes (serosae) – slick membranes that line ventral body cavity and cover organs in that cavity
• Endothelium – lines blood vessels• Mesothelium – lines body cavities and
mesenteries
Simple Cuboidal Epithelium
• Single layer/cube shape• Common in glands and their ducts• Ex. Salivary glands and pancreas,
walls of kidney tubules, covers surface of ovaries
Tubule lining –
longitudinal cut
Tubule lining – cross-section
Simple Columnar Epithelium• Single layer/column (tall) shape
• Often have goblet cells – produce lubricating mucus
• Ex: lines entire length of digestive tract from stomach to anus
• Mucosae (mucous membranes): epithelial membranes that line body cavities open to the body exterior
Pseudostratified Columnar Epithelium
• Appear to be multi-layered, but are actually one single layer that rest on the basement membrane
• Nuclei appear at different heights and some cells shorter than others
• Mainly functions in absorption and secretion
• Can be ciliated (pseudostratified ciliated columnar epithelium)
• Also can have goblet cells• Ex: respiratory tract – mucus produced
by goblet cells in this epithelium traps dust and other debris, and the cilia propel the mucus upward and away from the lungs
Stratified Squamous Epithelium
• Multiple layers, flat shape• Most common stratified epithelium in
body• Cells at free edge are squamous, and
those close to basement membrane can be cuboidal or columnar
• Found in sites that receive a good deal of abuse or friction
• Keratin – protein coating on apical surface (i.e. skin)– Can be keratinized or non-keratinized
• Ex. Esophagus, mouth, outer portion of skin
Non-keratinized
Keratinized
Stratified Cuboidal Epithelium• Two cell layers with (at least) the surface
cells being cuboidal in shape• Fairly rare in body; distribution
extremely limited• Mainly in ducts of large glands (larger
ducts of mammary glands, sweat and salivary glands, pancreas)
Stratified Columnar Epithelium• Multiple layers/Columnar cells
• Basal cells vary in size and shape, see multiple nuclei
• Even less common in body; distribution extremely limited
• Mainly in ducts of large glands• Ex. Urethra, pharynx
Transitional Epithelium
• Variable shapes• Highly modified, sratified squamous
epithelium that forms the lining of only a few organs– Urinary bladder, ureters, and part of the
urethra• Subject to considerable stretching• Cells of basal layer cuboidal or
columnar & cells at free surface vary in appearance
• Not stretched: superficial cells rounded and domelike
• Distended: epithelium thins and surface cells flatten and become squamouslike
Distended
Glandular Epithelium• Gland: one or more cells that make
and secrete a particular product• Secretion: typically contains protein
molecules in an aqueous fluid• Endocrine glands: ductless glands;
secretions (hormones) diffuse directly into the blood vessels that weave through the glands (i.e. thyroid, adrenals, pituitary)
• Exocrine glands: ducts; secretions empty through ducts to epithelial surface (i.e. sweat & oil glands, liver, pancreas)
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Connective Tissue• Connects body parts• Found everywhere in body• Most abundant and widely distributed
tissue• Primary functions:
– Protecting– Supporting– Binding together body
tissues
Connective Tissue Characteristics• Three basic elements: cells, ground
substance, fibers– Extracellular matrix: ground substance +
fibers• Fibers made of protein (collagen is most
abundant protein in body – 25%)• No free surface (connects!)• Has nerve supply (except cartilage)• Highly vascular
– except cartilage (avascular) & tendon (poorly vascularized)
• Matrix may be fluid, semifluid, gelatinous, fibrous, or calcified (depends on ground substance)– Secreted by connective tissue cells &
adjacent cells– ground substance: structureless; water plus
some adhesion proteins & large, charged, polysaccharide molecules
– Determines tissue’s qualities
Embryonic Origin • Mesenchyme: undifferentiated
connective tissue cells in embryo• All Connective tissue is derived from
mesoderm!!– How is this different from Epithelial
tissue?
Embryonic Connective Tissue• Embryo (0-2 months); Fetus (2 mos.-birth)
• Mesenchyme: almost exclusively in embryo; tissue from which all connective tissue will eventually arise
• Mucous (Wharton’s Jelly): umbilical cord of fetus – gives support
Connective Tissue Cells• Mesenchymal cells become blast cells (immature)
• Blast cells undergo mitosis and secrete the matrix• Mature cells do not divide & make matrix – just
maintain what is there
Connective Tissue Fibers• Type of fiber depends on type of tissue
• Fibers made of proteins• Types of fibers:
– Collagen fibers – tough & resistant to stretching/pulling forces; bone, cartilage, tendons, ligaments
– Elastic fibers – strength & stretching; skin, blood vessels, lungs (smaller than collagen fibers)
– Reticular fibers – collagen + glycoprotein; support in blood vessel walls & form strong supporting network around fat cells, nerve fibers, skeletal/smooth muscle fibers; form basement membrane and framework of soft organs
Types of Connective Tissue
• All CT consist of living cells surrounded by a matrix
• Differences: special cell types, fiber types, # of fibers
• Types:• Bone (Osseous)• Cartilage
• Hyaline cartilage
• Fibrocartilage• Elastic cartilage
• Dense Connective• Dense regular• Dense irregular• Dense elastic
• Loose Connective• Loose areolar• Adipose
• Loose reticular• Blood
Connective Tissue ID QuizTissue types:
• Loose areolar• Adipose• Dense connective• Cartilage• Bone• Blood
Parts:
• Fibroblast• Fibers• Nucleus• Adipocyte• Lipids (fats)• Chondrocyte• Lacuna(e)• Osteocyte• Canaliculi• Haversian system
(osteon)• Red blood cell
(erythrocyte)• White blood cell
(leukocyte)• Platelet (thrombocyte)
Bone (Osseous Tissue)• composed of osteocytes (bone cells) sitting in
lacunae (pits)• Surrounded by layers of very hard matrix of
calcium salts & collagen fibers• Exceptional ability to protect & support other
body organs– Great strength & some flexibility
• Movement, storing minerals, houses blood-forming tissue, stores lipids (yellow marrow)
• Parts: – haversian system (osteon) – basic unit– canaliculi – small canals that supply nutrients– central canal – contains blood vessels and nerves– Periosteum surrounds central canal – made of dense
irregular CT– Lamellae – rings of matrix (mineral salts & collagen)
p. 139 – Bone chapter
Cartilage• Less hard and more flexible than bone• Chondrocyte: cartilage cells• Hyaline cartilage (most widespread)
– Abundant collagen fibers hidden by a rubbery matrix with a glassy, blue-white appearance
– Supporting structures of larynx (voice box), attaches ribs to the breastbone, and covers the ends of many bones where they form joints
– Makes up the fetal skeleton– Epiphyseal (growth) plates in long bones during
youth• Fibrocartilage
– Highly compressible, forms the cushionlike disks between the vertebrae of the spinal column
• Elastic Cartilage– Found in structures with elasticity– Supports external ear
Hyaline Cartilage• No blood vessels (except perichondrium)
Fibrocartilage• Bundles of collagen in matrix• Pubic symphysis, intervertebral discs, meniscus
of knee• Support & fusion• No perichondrium• Strongest type: strength & rigidity
Elastic Cartilage• Threadlike fibers in gel matrix• Support & maintains shape• Has perichondrium• Similar to hyaline, but more elastic fibers
– Strength & exceptional stretchability• Epiglottis (“lid” on larynx), auditory tubes
Dense Connective Tissue• Also called dense fibrous tissue
• Collagen fibers are main matrix element• Fibroblasts (fiber-forming cells) manufacture
the building blocks of the fibers• Forms long, ropelike structures
– Tendons: attach skeletal muscles to bones– Ligaments: connect bones to bones at joints
(contain more elastic fibers than tendons)• Also makes up lower layers of skin (dermis)• Types:
– Dense Regular– Dense Irregular– Dense Elastic
Dense Regular Connective Tissue• Closely packed bundles of collagen fibers
running in same direction – fibers regular and parallel
• Great resistance to tension• Crowded between collagen fibers are
fibroblasts that make fibers & ground substance
• Found in tendons, ligaments, aponeuroses, and fascia
Dense Irregular Connective Tissue• Randomly arranged collagen fibers & few
fibroblasts• Fascia, dermis of skin, periosteum,
perichondrium, joint capsules, membrane capsules around organs, heart valves
• Provides strength• Places where pulling in various directions
occurs (found in sheets)• Same structural elements as dense regular, just
arranged irregularly and with thicker fibers
Dense Elastic Connective Tissue• Elastic fibers & fibroblasts
• Allows stretching of various organs and elasticity (returns to original shape)
• Lungs, walls of trachea, arteries, bronchial tubes, true vocal cords, and some ligaments
Loose Connective Tissue• Softer, more cells and fewer fibers than any
other connective tissue type (*except blood)• Types:
– Areolar Tissue– Adipose Tissue– Reticular Connective Tissue
Loose Areolar Connective Tissue• All three types of fibers, semi-fluid ground
substance, several cells• Most widely distributed connective tissue• Soft, pliable – cushions and protects body
organs• Universal packing tissue and connective tissue
“glue”– Holds organs together and in proper positions
• Reservoir of water and salts for surrounding tissues – All cells obtain nutrients from & release wastes into
this “tissue fluid”• Edema: areolar tissue in area soaks up excess
fluid when area is inflamed – area swells and becomes puffy
• Phagocytes scavenge for bacteria and debris and dead cells in this tissue to destroy
Adipose Tissue• Commonly called fat• Adipocytes: specialized to store triglycerides• Droplet of oil occupies most of fat cell &
compresses nucleus• Subcutaneous tissue beneath skin – insulates
body and protects from bumps and extremes of heat & cold
• Cushions individual organs and stores fat for fuel if needed
• Newborns – brown fat (rich blood supply & more mitochondria)– Helps them maintain body temperature
Loose Reticular Connective Tissue• Made of reticular cells (resemble fibroblasts) &
reticular fibers• Limited to certain sites – forms “stroma”
– internal framework that supports free blood cells (lymphocytes) in lymphoid organs (i.e. lymph nodes, liver, spleen, bone marrow)
• Binds together smooth muscle
Blood (Vascular Tissue)• Plasma + formed elements (erythrocytes,
leukocytes, thrombocytes)• Blood plasma = nonliving, fluid matrix
– “fibers” – soluble protein molecules that are visible only during blood clotting
• Transport vehicle for cardivoascular system– Carries nutrients, wastes & respiratory gases;
immunity; clotting
Muscle Tissue• Highly specialized to contract and produce
movement• Types of muscle tissue:
– Skeletal Muscle– Cardiac Muscle– Smooth Muscle
Muscle & Nervous Tissue ID Quiz
Tissue types:• Skeletal muscle• Cardiac muscle• Smooth muscle• Nervous tissue
Parts:• Nucleus• Striations
(bands)• Intercalated disc• Neuron• Cell body• Dendrite• Axon• Neuroglia
Skeletal Muscle Tissue• Packaged by connective tissue sheets into organs• Attached to bones• Controlled movements/voluntary movements• Muscular System• Cells are long, cylindrical, multinucleate, have
striations (stripes)• Cells called “muscle fibers” because they are
elongated• Fibers run parallel to each other• Function: Motion, maintenance of posture, heat
production (maintaining temperature)
Cardiac Muscle Tissue• Only in heart wall• Function: pump and propel blood• Involuntary• Striations, uninucleate• relatively short, branching cells that fit tightly
together at intercalated discs (attach cells end to end)
• Contain gap junctions that allow ions to pass freely from cell to cell resulting in rapid conduction of electrical impulse across the heart
Smooth Muscle Tissue• no striations visible• Involuntary muscle • Single nucleus, spindle-shaped (pointed at each
end)• Stomach, uterus, blood vessels, airways, walls of
hollow organs (viscera) i.e. urinary & gall bladder– Contracts: cavity becomes smaller (constriction)– Relaxes: cavity dilates and enlarges (dilation)
• Peristalsis – wavelike motion keeps food moving through small intestine
• Contracts more slowly than other types
Nervous Tissue• Internal communication• Found in brain, spinal cord, and nerves• Two types of cells:
– Neurons: receive and conduct electrochemical impulses from one part of the body to another
– Neuroglia: supporting cells that insulate, support, and protect delicate neurons within the structures of the nervous system
Neurons• Receive & conduct electrochemical impulses• Two functional characteristics:
– Irritability– Conductivity
• Cytoplasm drawn out into long processes• Parts:
– Cell body – nucleus & organelles– Dendrites – processes that receive impulse– Axons – process(es) that send impulse
Neuroglia• Supporting cells of the nervous tissue• Don’t generate nerve impulse• Often sites of tumors because they can divide• Insulate, support, protect neurons
Tissue Repair (Wound Healing)• Tissue injury stimulates the body’s
inflammatory and immune responses and healing begins almost immediately
• Returning to homeostasis• Tissue repair/wound healing occurs in two
ways:– Regeneration – replacement of destroyed tissue
by the same kind of cells (parenchyma cells – functioning cells of organ)
– Fibrosis – repair by dense (fibrous) connective tissue (scar tissue) – (stroma – supporting cells of organ – connective tissue)
– Which type depends on:• Type of tissue damaged• Severity of injury
• Different tissue types have different capacities for renewal of parenchyma cells– During embryonic development, muscle & nervous
become highly differentiated and lose capacity for mitosis; epithelial and connective tissues general have a capacity for renewal
Tissue Repair (Wound Healing)1. Inflammation
– Nonspecific body response that tries to prevent further injury
– Inflammatory chemicals are released and make capillaries permeable
– Fluid with clotting proteins seep into injured area from blood
– Clot is constructed to stop loss of blood and hold wound together
– Scab forms where clot is exposed to air
Tissue Repair (Wound Healing)2. Granulation Tissue
– Delicate pink tissue composed largely of new capillaries
– Grow into damaged area from undamaged blood vessels nearby
– Fragile & bleed freely (i.e. when scab picked)– Contains phagocytes that dispose of blood clot– Contains connective tissue cells (fibroblasts) that
produce the building blocks of collagen fibers (scar tissue) to permanently bridge the gap
Tissue Repair (Wound Healing)3. Regeneration & Fibrosis
– Surface epithelium regenerates across the granulation tissue below the scab
– Scab detaches when surface epithelium has covered wound
– Fibrosis (scar) usually underneath regenerated epithelium
• Scar Tissue: strong, lacks flexibility, in ability to perform normal tissue functions
• Adhesions can resultfrom fibrosis and cause abnormal joining of adjacent tissue (recentsurgery sites) – can causeobstructions (abdomen)
Tissue Repair (Wound Healing)• Tissue repair can be affected by:
– Nutrition– Blood circulation
• Transport of oxygen, nutrients, antibodies, etc.• Removal of tissue fluids, bacteria, and debris
– Age• Young are better nutritionally• Better blood supply• Cells have higher metabolic rate• Cells & extracellular components change with age• Collagen/elastic fibers change with age