tissue level of organization dr. michael p. gillespie

Tissue Level of

Organization

Dr. Michael P. Gillespie

Tissue Types

• Four basic tissue types exist in the body.• 1. Epithelial tissue• 2. Connective tissue• 3. Muscle tissue• 4. Nervous tissue

2Dr. Michael P. Gillespie

Epithelial Tissue

• Epithelial tissue covers body surfaces and lines hollow organs, body cavities, and ducts. It also forms glands.


Connective Tissue

• Connective tissue protects and supports the body and its organs. Various types of connective tissue bind organs together, store energy reserves as fat, and help provide immunity to disease-causing organisms.


Muscle Tissue

• Muscle tissue generates the physical force needed to make body structures move.


Nervous Tissue

• Nervous tissue detects changes in a variety of conditions inside and outside the body and responds by generating nerve impulses and help maintain homeostasis.


Biopsy

• A biopsy (bio = life, -opsy = to view) is the removal of a sample of living tissue for microscopic examination.

• Used to diagnose disorders.

• Compared to normal tissue.

• Removed surgically or through needle and syringe.


Cell Junctions

• Cell junctions are contact points between the plasma membranes of tissue cells.

• Functions• Forming seals between cells.• Anchoring cells to one another or to

extracellular material.• Channels between cells in a tissue

(passage of ions and molecules).


Major Types of Cell Junctions

• Tight junctions

• Adherens junctions

• Desmosomes

• Hemidesmosomes

• Gap junctions


Adherens Junctions

• Help epithelial cells resist separation.

• Located in epithelial cells.


Desmosomes

• Attach cells to one another.

• Contribute to the stability of the cells and tissue.

• Found in the epidermis and between cardiac muscle cells.


Hemidesmosomes

• Hemi – half. Hemidesmosomes lack links to adjacent cells.

• Anchor cells to the basement membrane.


Gap Junctions

• Form fluid filled channels that connect adjacent cells.

• Ions and small molecules can diffuse from the cytosol of one cell to the next.

• Enable nerve impulses to travel more rapidly among cells.


Epithelial Tissue

• Cells arranged in continuous sheets.

• Avascular – without blood vessels.

• Exchange of substances occurs by diffusion.


Apical Surface

• Apical (free) surface – faces the body surface, a body cavity, the lumen (interior space) of an internal organ, or a tubular duct that receives secretions from cells.


Lateral Surfaces

• The lateral surfaces of an epithelial cell face adjacent cells.

• The lateral surfaces may contain tight junctions, adherens junctions, desmosomes, and gap junctions.


Basal Surface

• Opposite the apical surface.

• Anchored to the basement membrane.


Basement Membrane

• Attaches to and supports the epithelial layer.

• Restricts the passage of larger molecules between the epithelial layer and connective tissue.


Types of Epithelium

• Covering and lining epithelium• Forms the outer covering of skin and some

internal organs.• Forms the lining of blood vessels, ducts,

body cavities, and the interior of the respiratory, digestive, urinary, and reproductive systems.

• Glandular epithelium• Forms the secreting portion of glands (I.e.

thyroid, adrenal and sweat glands).


Classification of Epithelium

• Classified by the # of layers.

• Classified by the shapes of cells.


Arrangement of Cells in Layers

• Simple epithelium - single layer of cells• Functions in secretion and absorption

• Stratified epithelium – 2 or more layers of cells• Protects underlying tissues

• Pseudostratified epithelium – contains a single layer of cells, but the nuclei lie at different levels.• Some cells are ciliated or secrete mucus.


Cell Shapes

• Squamous cells• Flat, thin cells that allow for rapid movement of

substances through them.

• Cuboidal cells• As tall as they are wide. Function in secretion

or absorption. May have microvilli.

• Columnar cells• Taller than they are wide. Specialized for

secretion or absorption.

• Transitional cells• Change shape as organs stretch and collapse.


Types of Simple Epithelium

• Simple squamous epithelium

• Simple cuboidal epithelium

• Simple columnar epithelium• Nonciliated• Ciliated


Types of Stratified Epithelium

• Stratified squamous epithelium• Keratinized• Nonkeratinized

• Stratified cuboidal epithelium

• Stratified columnar epithelium

• Transitional epithelium


Pseudostratified Columnar Epithelium• Nonciliated

• Ciliated


Simple Squamous Epithelium

• Single layer cells.

• Flat cells.

• Location• Bowman’s capsule of kidneys• Air sacs of lungs• Lining of the heart• Lining of blood vessels• Lining of lymphatic vessels• Inner surface of the tympanic membrane


Simple Cuboidal Epithelium

• Single layer of cells.

• Cells have an equal height and width.

• Functions of secretion and absorption.

• Location• Surface of ovary• Kidney tubules• Ducts of many glands• Secreting portions of some glands


Simple Columnar Epithelium

• Single layer of cells.

• Cells are taller than they are wide.

• Location• Ciliated

• Upper respiratory tract• Uterine (Fallopian) tubes• Paranasal sinuses• Central canal of spinal cord

• Nonciliated• GI tract from stomach to anus• Ducts of many galnds• Gallbladder


Stratified Squamous Epithelium

• 2 or more layers of cells• Apical layers of cells are flat• Deep layers vary in shape from cuboidal to

columnar

• Keratinized and nonkeratinized forms

• Location• Keratinized lines the surface of the skin• Nonkeratinized lines wet surfaces such as

the mouth, esophagus, epiglottis, vagina and tongue


Stratified Cuboidal Epithelium

• 2 or more layers of cells

• Equal in height and width

• Location• Ducts of adult sweat glands and

esophageal glands• Part of male urethra


Stratified Columnar Epithelium


• Taller than they are wide

• Basal layer contains shortened, irregularly shaped cells

• Only the apical layer has columnar cells

• Location• Part of urethra• Excretory ducts of some glands (I.e.

esophageal)• Anal mucous membrane• Conjunctiva of the eye


Transitional Epithelium


• Variable in appearance

• Present in the urinary system

• Un-stretched it looks similar to stratified cuboidal epithelium

• Stretched it looks similar to stratified squamous epithelium

• Location• Urinary bladder• Portions of the ureters and urethra


Pseudostratified Columnar Epithelium• Single layer of cells – appears to be more

than one layer due to uneven nuclei

• Some cells do not extend to the surface

• The cells that extend to the surface either secrete mucous (goblet cells) or bear cilia

• Location• Airways of the upper respiratory tract• Larger ducts of many glands• Epididymis• Part of male urethra


Glandular Epithelium

• Function – secretion

• Gland – a single cell or group of cells that secrete substances into ducts, onto a surface, or into the blood.

• 2 types• Endocrine• Exocrine


Endocrine Glands

• The secretions of endocrine glands enter the interstitial fluid and then diffuse directly into the bloodstream.

• These secretions do NOT flow through a duct.

• These secretions are called hormones.

• Examples• Pituitary, thyroid, and adrenal glands


Exocrine Glands

• Exocrine glands secrete their products into ducts that empty onto the surface of a covering and lining epithelium.

• Types of secretions• Mucus, sweat, oil, earwax, sailva,

digestive enzymes

• Examples• Sudoriferous (sweat) and salivary

glands


Structural Classification of

Glands• Unicellular – single celled

• Multicellular – many celled – distinct organ

• Simple - unbranched

• Compound - branched

• Tubular – tubular secretory parts

• Acinar – rounded secretory portions

• Tubular Acinar


Simple Glands

• Simple tubular• Glands in Large Intestine

• Simple branched tubular• Gastric glands

• Simple coiled tubular• Sweat glands

• Simple acinar• Glands of penile urethra

• Simple branched acinar• Sebaceous glands


Compound Glands

• Compound tubular• Bulbourethral (Cowper’s) glands

• Compound acinar• Mammary glands

• Compound tubuloacinar• Acinar glands of the pancreas


Functional Classification of Exocrine Glands

• Merocrine glands• The secretion is synthesizes on ribosomes on the

RER• Released from the cell in secretory vesicles• Most glands of the body

• Apocrine glands• Accumulate secretory products on the apical

surface, which then pinches off.

• Holocrine glands• Accumulate a secretory product in their cytosol.

The cell matures and ruptures, thus releasing its secretory product.


Connective Tissue Functions

• Binds together, supports, and strengthens other body tissues

• Protects and insulates internal organs

• Compartmentalizes structures such as skeletal muscles

• Major transport system within the body (blood is a fluid CT)

• Major site of stored energy reserves (adipose tissue)

• Main site of immune responses


Features of Connective Tissue

• 2 Basic element• Cells• Matrix

• Fills the wide spaces between the cells• Determines the tissue’s qualities

• In cartilage it is pliable• In bone it is hard and not pliable


Features of CT continued…

• Does not usually occur on body surfaces, with the exception of areolar which lines joint cavities.

• Usually highly vascular, with the exception of cartilage (avascular) and tendons (scanty).

• Contains a nerve supply with the exception of cartilage.


Types of CT Cells

• Fibroblasts

• Macrophages

• Plasma cells

• Mast cells

• Adipocytes

• White blood cells


Fibroblasts

• Fibro = fibers

• Secrete fibers and ground substance of the matrix


Macrophages

• Macro = large; -phages = eaters

• Develop from monocytes (type of WBC)

• Engulf bacteria and cellular debris by phagocytosis

• Fixed macrophages – reside in a particular tissue

• Wandering macrophages – roam tissues and gather at sites of infection or inflammation


Plasma Cells

• Develop from WBCs

• Secrete antibodies which attack foreign substances in the body

• Part of the immune system


Mast Cells

• Produce histamine which dilates small blood vessels

• Part of the inflammatory response

• Reaction to injury or infection


Adipocytes

• Adipose cells (fat cells)

• Store triglycerides (fats)

• Found below the skin and around organs such as the heart and kidneys


White Blood Cells

• Migrate to CT under certain conditions

• Neutrophils – respond to infection

• Eosinophils – respond to parasites and allergic responses


Connective Tissue Matrix

• Ground Substance• Supports cells, binds them together, and

provides a medium for the exchange of substances

• Fibers• Strengthen and support CTs• Types

• Collagen fibers – strong but not stiff (flexible)• Elastic fibers – smaller in diameter than collagen –

stretch and return to their original shape• Reticular fibers – support to walls of blood vessels, form

a network around tissues, form basement membrane


Marfan Syndrome

• An inherited disorder caused by a defective fibrillin gene

• Abnormal development of elastic fibers.

• Predominant structures affected:• Periosteum of the bones• Ligament that suspends the lens of the eye• Walls of large arteries

• Features:• Tall with disproportionately long arms, legs, and digits• Blurred vision from displacement of the lens• Weakening of the aorta (susceptible to burst)


Classification of Connective Tissue

• Embryonic CT – present in the embryo and fetus• Mesenchyme – all CT arises from this• Mucous CT (Wharton’s jelly) – umbilical cord

• Mature CT – present in the newborn• Loose CT• Dense CT• Cartilage• Bone Tissue• Blood Tissue• Lymph


Embryonic Connective Tissue

• Mesenchyme

• Mucous CT


Loose Connective Tissue

• Areolar CT

• Adipose Tissue

• Reticular CT


Dense Connective Tissue

• Dense regular CT

• Dense irregular CT

• Elastic CT


Cartilage

• Hyaline cartilage

• Fibrocartilage

• Elastic cartilage


Loose Connective Tissue

• The fibers are loosely intertwined and many cells are present


Areolar Connective Tissue

• Widely distributed throughout the body

• Contains fibroblasts, macrophages, plasma cells, mast cells, adipocytes, and WBCs

• Fiber types• Collagen, elastic, and reticular

• Combined with adipose tissue it forms the subcutaneous layer


Adipose Connective Tissue

• Loose CT

• Adipocytes (adipo = fat) – store triglycerides

• Good insulator

• Energy Reserve

• Supports and protects organs

• Cytoplasm and nucleus are pushed to the periphery of the cell from large triglyceride droplet

• New blood vessels form with new adipose tissue (can lead to hypertension)


Liposuction

• Lip = fat; suction lipectomy ectomy = to cut out

• Suctioning out small sections of adipose tissue

• Complications• Fat emboli (clots)• Fluid depletion• Injury to internal structures• Severe postoperative pain


Reticular Connective Tissue

• Forms the stroma (supporting framework) of the liver, spleen, and lymph nodes

• Binds together smooth muscle cells

• Reticular fibers in the spleen filter blood and remove worn-out blood cells

• Reticular fibers in the lymph nodes filter lymph and remove bacteria


Dense Connective Tissue

• More numerous, thicker, denser fibers and fewer cells than loose CT

• Dense Regular CT – tendons and most ligaments

• Dense Irregular CT – heart valves, perichondrium, periosteum

• Elastic CT – lung tissue, elastic arteries


Cartilage

• Dense network of cartilage fibers and elastic fibers

• Endures more stress than loose and dense CT

• Chondrocytes = mature cartilage cells


Hyaline Cartilage

• Most abundant cartilage in the body

• Weakest of the 3 types of cartilage

• Flexible

• Located in joints – reduces friction and shock


Fibrocartilage

• Strongest of the 3 types of cartilage

• Strength and rigidity

• Located in intervertebral discs


Elastic Cartilage

• Provides strength and elasticity

• Maintains the shape of external structures

• Located in the ear


Bone Tissue

• The basic unit of compact bone is an osteon or Haversian system

• 4 parts of the osteon• Lamellae = little plates – concentric rings of

matrix – consist of mineral salts• Lacunae = little lakes – spaces btwn. Lamellae

that contain osteocytes• Canaliculli = little canals – contain processes of

osteocytes – routes for nutrients and waste products

• Central (Haversian) canal – contains blood vessels and nerves


Blood Tissue

• Connective Tissue with a liquid matrix called blood plasma – pale yellow fluid (mostly water) with dissolved substances: nutrients, wastes, enzymes, plasma proteins, hormones, gases, ions

• Suspended• Red blood cells• White blood cells• Platelets


Lymph

• Extracellular fluid that flows in lymphatic vessels

• Contains lymphocytes (type of WBC) and dietary lipids


Elephantiasis


Membranes

• Flat sheets of pliable tissue that cover or line a part of the body

• Two types• Epithelial

• Mucous membrane• Serous membrane• Cutaneous membrane of the skin

• Synovial


Mucous Membranes

• Lines a body cavity that opens directly to the exterior

• Line digestive, respiratory, reproductive tracts and much of the urinary tract

• Goblet cells secrete mucous


Serous Membranes

• Serous = watery

• Line body cavities that do NOT open directly to the exterior

• Two layers• Parietal (pariet = wall) – attached to the cavity wall• Visceral (viscer = body organ) – attaches to the

organs inside the cavity

• Secretes serous fluid

• Pleura / pericardium / peritoneum


Synovial Membranes

• Syn = together

• Line the cavities of freely moveable joints

• Secrete synovial fluid which lubricates and nourishes the joint


Muscle Tissue

• Consists of elongated cells called muscle fibers

• Produces body movements, maintains posture, and generate heat

• Types• Skeletal muscle tissue• Cardiac muscle tissue • Smooth muscle tissue


Skeletal Muscle Tissue

• Attaches to bones of the skeleton

• Striated

• Voluntary


Cardiac Muscle Tissue

• Forms the wall of the heart

• Striated

• Involuntary

• Fibers attach to one another via intercalated discs (intercalat = to insert between)


Smooth Muscle Tissue

• Located in the walls of hollow internal structures

• Involuntary

• Lacks striations (smooth)

• Located in blood vessels, airways to lungs, stomach, intestines, gallbladder, and urinary bladder


Nervous Tissue

• Two types of cells• Neurons – nerve cells• Neuroglia (glia = glue) – supporting

structures

• Parts of Neurons• Cell body• Dendrites• Axon


tissue level of organization dr. michael p. gillespie

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