Chapter 4 Histology: the Study of Tissues

Chapter 04

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4-2 4.1 Tissues and Histology • Tissue classification based on structure of cells, composition of noncellular extracellular matrix, and cell function – Epithelial – Connective – Muscle – Nervous • Histology: Microscopic Study of Tissues – Biopsy: removal of tissues for diagnostic purposes – Autopsy: examination of organs of a dead body to determine cause of death

4-3 Epithelial Tissue Connective Tissue

Muscular Tissue Nervous Tissue

4-4 4.2 Embryonic Tissue • Germ layers – Endoderm • Inner layer • Forms lining of digestive tract and derivatives – Mesoderm • Middle layer • Forms tissues as such muscle, bone, blood vessels – Ectoderm • Outer layer • Forms skin and neuroectoderm

4-5 4.3 Epithelial Tissue • Consists almost entirely of

Free surface • Covers body surfaces and Lung Pleura Epithelial cells with little extracellular forms glands matrix – Outside surface of the body

LM 640x Surface view – Lining of digestive, respiratory Nucleus and urogenital systems

Basement membrane – Heart and blood vessels Connective tissue

Capillary – Linings of many body cavities • Has free, basal, and lateral LM 640x Cross-sectional view surfaces b: © Victor Eroschenko; c: © Ed Reschke • Basement membrane • Specialized cell contacts • Avascular

• Regenerate 4-6 Basement Membrane • Extracellular: formed by secretions of both epithelium and connective tissue. Acellular “glue” – Attachment to C.T. – Guides cell migration during tissue repair – Acts as a filter in the nephron of the kidney – Not every epithelium has a basement membrane associated with it

4-7 Functions of Epithelial Tissue

• Protecting underlying structures; e.g., epithelium lining the mouth • Acting as barriers; e.g., skin • Permitting the passage of substances; e.g., nephrons in kidney • Secreting substances; e.g., pancreas • Absorbing substances; e.g., lining of small intestine

4-8 Classification of Epithelium • Number of layers of cells – Simple- one layer of cells. Each extends from basement membrane to the free surface – Stratified- more than one layer. Shape of cells of the apical layer used to name the tissue. Includes transitional epithelium where the apical cell layers change shape depending upon distention of the organ which the tissue lines – Pseudostratified- tissue appears to be stratified, but all cells contact basement membrane so it is in fact simple • Shape of cells – Squamous- flat, scale-like – Cuboidal- about equal in height and width – Columnar- taller than wide 4-9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.1 Classification of Epithelium

Number of Layers or Category Shape of Cells

Simple (single layer of cells) Squamous Cuboidal Columnar

Stratified (more than one layer of cells) Squamous Nonkeratinized (moist) Keratinized Cuboidal (very rare) Columnar (very rare)

Pseudostratified (modification of Columnar simple epithelium)

Transitional (modification of Roughly cuboidal to columnar stratified epithelium) when not stretched and squamouslike when stretched

4-10 Functional Characteristics

• Simple: allows diffusion of gases, filtration of blood, secretion, absorption • Stratified: protection, particularly against abrasion • Squamous: allows diffusion or acts as filter • Cuboidal and columnar: secretion or absorption. May include goblet cells that produce and secrete mucus.

4-11 Free Surfaces

Free surfaces of epithelium • Smooth: reduce friction • Microvilli: increase surface area for absorption or secretion – Stereocilia: elongated microvilli for sensation and absorption • Cilia: move materials across the surface • Folds: in transitional epithelium where organ must be able to change shape. Urinary system.

4-12 Simple Squamous Epithelium • Structure: single layer of flat cells • Location: simple squamous- lining of blood and lymphatic vessels (endothelium) and small ducts, alveoli of the lungs, loop of Henle in kidney tubules, lining of serous membranes (mesothelium) and inner surface of the eardrum. • Functions: diffusion, filtration, some protection against friction, secretion, absorption.

TABLE 4.2 Simple Epithelium

(a) Simple Squamous Epithelium

Structure: Single layer of flat, often Function: Diffusion, filtration, Location: Lining of blood vessels hexagonal cells; the nuclei appear some secretion, and some and the heart, lymphatic vessels Kidney as bumps when viewed as a cross protection against friction (endothelium) and small ducts, section because the cells are so flat alveoli of the lungs, portions of the kidney tubules, lining of serous membranes (mesothelium) of the body cavities (pleural, pericardial, peritoneal), and inner surface of the tympanic membranes

Free surface

Nucleus

Basement membrane

Simple squamous epithelial cell 4-13 LM 640x

Simple Squamous squamous cell epithelium

Loose Nucleus of connective squamous cell tissue Simple Cuboidal Epithelium • Locations: Kidney tubules, glands and their ducts, choroid plexus of the brain, lining of terminal bronchioles of the lungs, and surface of the ovaries. • Structure: single layer of cube-shaped cells; some types have microvilli (kidney tubules) or cilia (terminal bronchioles of the lungs) • Functions: – Secretion and absorption in the kidney – Secretion in glands and choroid plexus – Movement of mucus out of the terminal bronchioles by ciliated cells.

TABLE 4.2 Simple Epithelium

(b) Simple Cuboidal Epithelium

Structure: Single layer of cube- Function: Secretion and absorption Location: Kidney tubules, glands shaped cells; some cells have by cells of the kidney tubules; and their ducts, choroid plexuses Kidney microvilli (kidney tubules) or cilia secretion by cells of glands and of the brain, lining of terminal (terminal bronchioles of the lungs) choroid plexuses; movement of bronchioles of the lungs, surfaces particles embedded in mucus of the ovaries out of the terminal bronchioles by ciliated cells

Free surface

Nucleus

Simple cuboidal epithelial cell

Basement membrane 4-15 LM 640x

Simple cuboidal Cuboidal cell epithelium

Lumen of Nucleus of cuboidal tubule cell Simple Columnar Epithelium • Location. Glands and some ducts, bronchioles of lungs, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts and ventricles of the brain. • Structure: single layer of tall, narrow cells. Some have cilia (bronchioles of lungs, auditory tubes, uterine tubes, and uterus) or microvilli (intestine). • Functions: – Movement of particles out of the bronchioles by ciliated cells – Aids in the movement of oocytes through the uterine tubes by ciliated cells – Secretion by glands of the stomach and the intestine – Absorption by cells of the intestine. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.2 Simple Epithelium—Continued

Structure: Single layer of tall, Function: Movement of particles Location: Glands and some ducts, narrow cells; some cells have cilia out of the bronchioles of the lungs bronchioles of the lungs, auditory Lining of (bronchioles of lungs, auditory by ciliated cells; partially responsible tubes, uterus, uterine tubes, stomach and tubes, uterine tubes, and uterus) for the movement of oocytes through stomach, intestines, gallbladder, intestines or microvilli (intestines) the uterine tubes by ciliated cells; bile ducts, ventricles of the brain secretion by cells of the glands, the stomach, and the intestines; absorption by cells of the small and large intestines

Free surface

Goblet cell containing mucus

Nucleus

Simple columnar epithelial cell 4-17 Basement LM 640x membrane

Simple columnar Basement membrane epithelium (ciliated)

Simple columnar Lamina propria cell (ciliated) Lumen of uterine tube Cilia Simple Columnar Epithelium (nonciliated)

Simple columnar Goblet cell epithelium

Simple columnar cell Lumen of jejenum Microvilli (brush border) Lamina propria Stratified Squamous Epithelium • Locations: – Moist- mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, and cornea – Keratinized- skin • Structure: multiple layers of cells that are cuboidal in the basal layer and progressively flatten toward the surface. In moist, surface cells retain a nucleus and cytoplasm. In keratinized, surface cells are dead. • Functions: protection against abrasion, caustic chemicals, water

loss, and infection. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.3 Stratified Epithelium (a) Stratified Squamous Epithelium Structure: Multiple layers of cells that Function: Protection against Location: Keratinized—primarily In Skin are cube-shaped in the basal layer and abrasion, a barrier against the skin; nonkeratinized—mouth, progressively flattened toward the surface; infection, reduction of water throat, larynx, esophagus, anus, Cornea the epithelium can be nonkeratinized (moist) loss from the body vagina, inferior urethra, cornea or keratinized; in nonkeratinized stratified Mouth squamous epithelium, the surface cells retain a nucleus and cytoplasm; in keratinized stratified epithelium, the cytoplasm of Esophagus cells at the surface is replaced by a protein called keratin, and the cells are dead

Free surface

Nonkeratinized stratified squamous epithelial cell

Nuclei

Basement membrane 4-20

LM 640x

Epidermis (Stratified squamous epithelium)

Dermis

Stratum Stratum Stratum Stratum spinosum granulosum corneum basale Stratified Squamous Epithelium (Nonkeratinized)

Stratified squamous epithelium (nonkeratinized)

Lamina propria

Squamous cell Stratified Cuboidal Epithelium

• Locations: sweat gland ducts, ovarian follicular cells, and salivary gland ducts • Structure: multiple layers of somewhat cube-shaped cells. • Functions: secretion, absorption and protection against infections. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.3 Stratified Epithelium—Continued

(b) Stratified Cuboidal Epithelium

Structure: Multiple layers of Function: Secretion, absorption, Location: Sweat gland ducts, somewhat cube-shaped cells protection against infection ovarian follicular cells, salivary gland ducts

Parotid gland duct Sublingual gland duct Submandibular gland duct

Free surface

Nucleus

Basement membrane

Stratified cuboidal epithelial LM 413x cell 4-23

b: © The McGraw-Hill Companies, Inc./Dr. Alvin Telser, photographer; Stratified Cuboidal Epithelium Stratified cuboidal Cuboidal cell

Lumen of parotid Venule duct Stratified Columnar Epithelium • Locations: mammary gland duct, larynx, portion of male urethra. • Structure: multiple layers of cells with tall thin cells resting on layers of more cuboidal cells. Cells ciliated in the larynx. • Function: protection and secretion. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.3 Stratified Epithelium—Continued (c) Stratified Columnar Epithelium Structure: Multiple layers of cells Function: Protection, secretion Location: Mammary gland ducts, with tall, thin cells resting on layers larynx, a portion of the male urethra of more cube-shaped cells; the cells are ciliated in the larynx Larynx

Free surface

Nucleus

Basement membrane

Stratified columnar epithelial LM 413x 4-25 cell

Stratified columnar Lamina epithelium propria

Lumen of spongy Columnar urethra cell Pseudostratified Columnar Epithelium • Locations: lining of nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi of lungs. • Structure: all cells reach basement membrane. Appears stratified because nuclei are at various levels. Almost always ciliated and associated with goblet (mucus-producing) cells. • Functions: – Synthesize and secrete mucus onto the free surface – Move mucus (or fluid) that contains foreign particles over the free surface and from passages Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.4 Pseudostratified Columnar Epithelium and Transitional Epithelium

(a) Pseudostratified Columnar Epithelium

Structure: Single layer of cells; Function: Synthesize and secrete Location: Lining of the nasal cavity, some cells are tall and thin and mucus onto the free surface; move nasal sinuses, auditory tubes, reach the free surface, and others mucus (or fluid) that contains pharynx, trachea, bronchi of do not; the nuclei of these cells foreign particles over the surface of the lungs Trachea are at different levels and appear the free surface and from passages stratified; the cells are almost Bronchus always ciliated and are associated with goblet cells that secrete mucus onto the free surface

Cilia

Free surface

Goblet cell containing mucus

Pseudostratified columnar epithelial cell

Nucleus

Basement membrane 4-27

LM 413x

a : © Victor Eroschenko Pseudostratified Columnar Epithelium Lumen of trachea

Pseudostratified Nucleus of basal columnar cell epithelium

Cilia Columnar epithelial cell (ciliated) Lamina propria Transitional Epithelium • Location: lining of urinary bladder, ureters and superior urethra. • Structure: stratified; cells change shape depending upon amount of distention of the organ. • Functions: accommodates fluctuations in the volume of fluid in an organ or tube; protection against the caustic effects of urine. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.4 Pseudostratified Columnar Epithelium and Transitional Epithelium (b) Transitional Epithelium Structure: Stratified cells that Function: Accommodate Location: Lining of the urinary appear cube-shaped when the fluctuations in the volume of fluid bladder, ureters, superior urethra organ or tube is not stretched and in organs or tubes; protect against squamous when the organ or tube the caustic effects of urine is stretched by fluid; the number of layers also decreases on stretch Ureter

Free surface

Transitional Urinary bladder epithelial cell Urethra

Nucleus

LM 413x Basement membrane

Free surface

T issue not stretched Transitional epithelial cell LM 413x

Nucleus

Basement membrane 4-29

T issue stretched

Transitional epithelium

Lamina propria

Luminal cells Blood capillary Transitional Epithelium Cross- LM: High Magnification section of ureter

Mucosa of ureter

Transitional epithelium of ureter Transitional Epithelium of Urinary Bladder LM: High Magnification Transitional epithelium of bladder Detrusor muscle

TABLE 4.5 Function and Location of Epithelial Tissue

LOCATION

Simple Squamous Simple Cuboidal Simple Columnar Stratified Squamous Stratified Cuboidal Stratified Columnar Pseudostratifie Transitional Function Epithelium Epithelium Epithelium Epithelium Epithelium Epithelium Columnar Epithelium Epithelium Diffusion Blood and lymphatic capillaries, alveoli of lungs, thin segments of loops of Henle Filtration Bowman capsules of kidneys Secretion or Mesothelium Choroid plexus Stomach, small absorption (serous fluid) (produces cerebrospinal intestine, large fluid), part of kidney intestine, uterus, tubules, many glands many glands and their ducts Protection Endothelium Skin (epidermis), (against friction (e.g., epithelium corneas, mouth and and abrasion) of blood vessels) throat, epiglottis, Mesothelium larynx, esophagus, (e.g., epithelium anus, vagina of body cavities)

Movement Terminal bronchioles Bronchioles of lungs, larynx, nasal cavity, of mucus of lungs auditory tubes, uterine paranasal sinuses, (ciliated) tubes, uterus nasopharynx, auditory tubes, trachea, bronchi of lungs Capable Urinary bladder, of great ureter, superior stretching part of urethra Miscellaneous Inner part of tympanic Surface of ovaries, Bile duct, gallbladder, Lower part of urethra, Sweat gland ducts Part of male urethra, Part of male urethra, membranes, smallest inside lining of eyes ependyma (lining of sebaceous gland ducts epididymides, ductus salivary gland ducts ducts of glands (pigmented epithelium brain ventricles and deferens, mammary of retina), ducts of central canal of spinal gland ducts glands cord), ducts of glands

4-33 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cell Connections Free surface • Found on lateral and basal surfaces of cells Tight junction • Functions Adhesion belt – Form permeability layer Actin – Bind cells together filaments – Provide mechanism for Channel Desmosome intercellular communication Gap junction • Types Intermediate – Desmosomes filaments – Tight junctions – Gap junctions

Hemidesmosome

Basement membrane 4-34 Cell Connections • Desmosomes: disk-shaped regions of cell membrane; often found in areas that are subjected to stress. – Contain especially adhesive glycoproteins. – Intermediate protein filaments extend into cytoplasm of cells. – Striated squamous epithelium of the skin. • Hemidesmosomes: half of a desmosome; attach epithelial cells to basement membrane. • Tight Junctions: hold cells together, form permeability barrier. – zonula adherens: between adjacent cells, weak glue, hold cells together. Simple epithelium. – zonula occludens: permeability barrier, e.g., stomach and urinary bladder, chemicals cannot pass between cells. • Gap Junctions: protein channels aid intercellular communication. – Allows ions and small molecules to pass through. – Coordinate function of cardiac and smooth muscle. – May help coordinate movement of cilia in ciliated types of epithelium. 4-35 Glands • Epithelium with supporting network of C.T. • Two types of glands formed by infolding of epithelium: – Endocrine: no open contact with exterior; no ducts; produce hormones – Exocrine: open contact maintained with exterior; ducts • Exocrine glands classified either by structure or by the method of secretion • Classified by structure – Unicellular: goblet cells – Multicellular

4-36 Goblet Cells

Goblet cells

Trachea 4-37 Multicellular Exocrine Glands

Single gland cell • Types of ducts in epithelium Unicellular (goblet cells in large and small – Simple: ducts with few intestine and respiratory passages)

branches Duct

Secretory – Compound: ducts with portion many branches Simple tubular Simple branched tubular Simple coiled tubular Simple acinar Simple branched acinar (glands in stomach (glands in lower portion (lower portion of stomach (sebaceous glands (sebaceous glands of skin) and colon) of stomach) and small intestine) of skin)

• If ducts end in tubules (a) Simple glands or sac-like structures: acini. Pancreas Duct Secretory portions • If ducts end in simple

Compound tubular Compound acinar Compound tubuloacinar sacs: alveoli. Lungs (mucous glands of duodenum) (mammary glands) (pancreas)

(b) Compound glands

4-38 Merocrine Sweat Gland

4-39 Apocrine sweat gland Epithelium of apocrine sweat gland Lumen

4-40 Method of Secretion Types

Dying cell releases Pinched-off portion secretory products Secretion in duct of cell in the secretion

Vesicle releasing contents into duct

Replacement cell Vesicle containing secretory products

Secretory products Cell shed into stored in the cell the duct

(a) Merocrine gland (b) Apocrine gland (c) Holocrine gland Cells of the gland produce secretions by Secretory products are stored in the cell near Secretory products are stored in the active transport or produce vesicles that the lumen of the duct. A portion of the cell cells of the gland. Entire cells are shed contain secretory products, and the vesicles near the lumen containing secretory products by the gland and become part of the empty their contents into the duct through is pinched off the cell and joins secretions secretion. The lost cells are replaced exocytosis. produced by a merocine process. by other cells deeper in the gland.

4-41 4.4 Connective Tissue

• Abundant; found in every organ • Consists of cells separated by extracellular matrix • Many diverse types • Performs variety of important functions

Embryonic Connective Tissue Mesenchyme Mucous connective tissue Adult Connective Tissue Connective Tissue Proper Loose (fewer fiber, more ground substance) Areolar Adipose Reticular Dense (more fiber, less ground substance) Dense, regular collagenous Dense, regular elastic Dense, irregular collagenous Dense, irregular elastic SupportingConnectiveTissue Cartilage (semisolidmatrix) Hyaline Fibrocartilage Elastic Bone (solid matrix) Spongy Compact Fluid Connective Tissue Blood Red blood cells White blood cells Platelets Hemopoietic tissue Red marrow Yellow marrow 4-43 Functions of Connective Tissue

• Enclose organs as a capsule and separate organs into layers • Connect tissues to one another. Tendons and ligaments. • Support and movement. Bones. • Storage. Fat. • Cushion and insulate. Fat. • Transport. Blood. • Protect. Cells of the immune system.

4-44 Cells of Connective Tissue

• Specialized cells produce the extracellular matrix • Descriptive word stems – Blasts: create the matrix, example osteoblast – Cytes: maintain the matrix, example chondrocyte – Clasts: break the matrix down for remodeling, example osteoclasts

4-45 Cells of Connective Tissue • Adipose or fat cells (adipocytes). Common in some tissues (dermis of skin); rare in some (cartilage) • Mast cells. Common beneath membranes; along small blood vessels. Can release heparin, histamine, and proteolytic enzymes in response to injury. • White blood cells (leukocytes). Respond to injury or infection • Macrophages. Phagocytize or provide protection – Fixed: stay in position in connective tissue – Wandering: move by amoeboid movement through the connective tissue • Platelets. Fragments of hematopoietic cells involved in clotting. • Undifferentiated mesenchyme (stem cells). Have potential to differentiate into adult cell types. 4-46 Extracellular Matrix • Protein fibers of the matrix – Collagen. Most common protein in body; strong, flexible, inelastic – Reticular. Fill spaces between tissues and organs. Fine collagenous, form branching networks – Elastic. Returns to its original shape after distension or compression. Contains molecules of protein elastin that resemble coiled springs; molecules are cross-linked

4-47 Other Matrix Molecules

Most common molecules are called the ground substance and include: – Hyaluronic acid: polysaccharide. Good lubricant. Vitreous humor of eye. – Proteoglycans: protein and polysaccharide. Protein part attaches to hyaluronic acid. Trap large amounts of water. – Adhesive molecules: hold proteoglycan aggregates together. Chondronectin in cartilage, osteonectin in bone, fibronectin in fibrous connective tissue.

Collagen fiber

(a) Collagen fibers.

Polypeptide chains

Linked

Stretched

Relaxed

Stretched elastin Recoiled elastin (b) Elastic fibers

Hyaluronic acid Link protein

Protein core Chondroitin sulfate Water

Structure: The mesenchymal cells are Location: Mesenchyme is the embryonic tissue irregularly shaped; the extracellular matrix from which connective tissues, as well as other is abundant and contains scattered reticular tissues, arise fibers • Mesenchyme: source of all adult connective tissue. Intercellular matrix – Forms primarily from Nuclei of mesenchyme cells mesoderm

LM 200x – Delicate collagen fibers

(b) Mucous Connective Tissue embedded in semi-fluid

Structure: Mucous tissue is mesenchymal Location: Umbilical cord of newborn tissue that remains unspecialized; the cells matrix are irregularly shaped; the extracellular matrix is abundant and contains scattered Umbilical reticular fibers cord • Mucus: found only in the

Intercellular matrix umbilical cord. Wharton’s

Nuclei of mucous connective jelly. tissue cells

LM 200x

a-b: © Victor Eroschenko 4-50 Adult Connective Tissues • Connective Tissue Proper – Loose (areolar). Collagenous fibers are loosely arranged – Dense. Fibers form thick bundles that nearly fill all extracellular space • Supporting CT – Cartilage – Bone • Fluid CT

– Blood 4-51 Loose (Areolar) Connective Tissue

TABLE 4.8 Connective Tissue Proper: Loose Connective Tissue

(a) Areolar Connective Tissue

Structure: Cells (e.g., fibroblasts, macrophages, and Function: Loose packing, support, and Location: Widely distributed throughout the body; lymphocytes) within a fine network of mostly nourishment for the structures with substance on which epithelial basement membranes rest; collagen fibers; often merges with denser which it is associated packing between glands, muscles, and nerves; attaches connective tissue the skin to underlying tissues

Epidermis Nucleus Elastic fiber Skin Dermis

Collagen fiber Loose connective tissue

Muscle LM 400x Fat

a:© Ed Reschke • Loose packing material of most organs and tissues, also known as stroma • Attaches skin to underlying tissues. Superficial fascia = subcutaneous layer = hypodermis • Contains collagen, reticular, elastic fibers and all five types of cells • Often seen in association with other types of C.T., like reticular tissue and fat • Cells include fibroblasts, mast cells, lymphocytes, adipose cells, 4-52 macrophages Areolar Connective Collagen fibers Tissue

Ground substance Elastic fibers

Capillary Endothelial cell of capillary Mast cell Nucleus of with granules fibroblasts Connective Tissue with Special Properties: Adipose Predominant cells are adipocytes • Yellow (white). Most abundant type, has

a wide distribution. White at birth and Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.8 Connective Tissue Proper: Loose Connective Tissue yellows with age. (b) Adipose Tissue Structure: Little extracellular matrix surrounding Function: Packing material, thermal Location: Predominantly in subcutaneous areas, in cells; the adipocytes are so full of lipid that the insulation, energy storage, and protection mesenteries, in renal pelvis, around kidneys, attached to cytoplasm is pushed to the periphery of the cell of organs against injury from being the surface of the colon, in mammary glands, in loose – Carotenes come from plants and can bumped or jarred connective tissue that penetrates spaces and crevices be metabolized into vitamin A. Adipose tissue

Nucleus Mammary – Scant ring of cytoplasm surrounding gland

Adipocytes single large lipid droplet. Nuclei or fat cells

flattened and eccentric. LM 100x • Brown. Found only in specific areas of © Carolina Biological Supply/Phototake.com body: axillae, neck and near kidneys – Cells are polygonal in shape, have a considerable volume of cytoplasm and contain multiple lipid droplets of varying size. Nuclei are round and almost centrally located. 4-54

Adipose Connective Tissue

Adipocytes Lipid inclusions of adipocytes

Nuclei of Capillaries adipocytes Connective Tissue with Special Properties: Reticular Tissue • Forms superstructure of lymphatic and hemopoietic tissues • Network of fine reticular fibers and reticular cells. • Spaces between cells contain white cells and dendritic cells

TABLE 4.8 Connective Tissue Proper: Loose Connective Tissue

Structure: Fine network of reticular fibers Function: Provides a superstructure for Location: Within the lymph nodes, spleen, bone marrow irregularly arranged lymphatic and hemopoietic tissues Leukocytes

Reticular fibers

Lymph node

Spleen

LM 280x 4-56

Reticular Ground fibers substance

Leukocytes Macrophage s Dense Regular Collagenous Connective Tissue

• Has abundant collagen

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. fibers that resist TABLE 4.9 Connective Tissue Proper: Dense Connective Tissue (a) Dense Regular Collagenous Connective Tissue stretching Structure: Matrix composed of collagen Function: Able to withstand great pulling Location: Tendons (attach muscle to bone) and ligaments fibers running in somewhat the same forces exerted in the direction of fiber (attach bones to each other) direction orientation; great tensile strength and – Tendons: Connect stretch resistance Ligament Nucleus of Tendon muscles to bones; fibroblast Collagen fibers are not fibers necessarily parallel – Ligaments: Connect bones to bones. LM 165x LM 1000x a1: © Victor Eroschenko; a2: © Ed Reschke/Peter Arnold, Inc. Collagen often less compact, usually flattened, form sheets or bands 4-58 Dense Regular Connective Tissue

TABLE 4.9 Connective Tissue Proper: Dense Connective Tissue

(b) Dense Regular Elastic Connective Tissue

Structure: Matrix composed of regularly Function: Able to stretch and recoil like a rubber band, Location: Vocal folds and elastic ligaments between arranged collagen fibers and elastic fibers with strength in the direction of fiber orientation the vertebrae and along the dorsal aspect of the neck

Base of tongue Vocal folds (true vocal cords)

Elastic Vestibular fold fibers (false vocal cord) Nucleus of fibroblast

LM 100x LM 200x

© Victor Eroschenko • Ligaments in vocal folds; nuchal ligament • Collagen fibers give strength (for when you shout), but elastic fibers are more prevalent 4-60 Dense Irregular Collagenous Connective Tissue • Protein fibers arranged in a randomly oriented network • Forms innermost layer of the dermis of the skin, scars, capsules of kidney and spleen

TABLE 4.9 Connective Tissue Proper: Dense Connective Tissue—Continued

Structure: Matrix composed of collagen fibers Function: Tensile strength capable of withstanding Location: Sheaths; most of the dermis of the skin; that run in all directions or in alternating planes stretching in all directions organ capsules and septa; outer covering of body of fibers oriented in a somewhat single direction tubes

Epidermis Epidermis Skin

Dermis

Dense irregular Loose connective collagenous tissue connective tissue of dermis Muscle LM 100x LM 250x Fat

Collagen fibers Ground substance Nuclei of fibroblasts Dense Irregular Elastic Connective Tissue

TABLE 4.9 Connective Tissue Proper: Dense Connective Tissue

(d) Dense Irregular Elastic Connective Tissue

Structure: Matrix composed of bundles and Function: Capable of strength, with stretching and Location: Elastic arteries sheets of collagenous and elastic fibers oriented recoil in several directions in multiple directions

Dense irregular elastic connective tissue Aorta

LM 265x LM 100x

Lumen of Elastic elastic artery lamellae

Nuclei of Endothelium fibroblasts of elastic artery

Nuclei of Tunica intima Tunica media Internal smooth of elastic of elastic elastic muscle cells artery artery lamella Supporting Connective Tissue: Cartilage

• Composed of chondrocytes located in matrix-surrounded spaces called lacunae. • Type of cartilage determined by components of the matrix. • Firm consistency. • Ground substance: Proteoglycans and hyaluronic acid complexed together trap large amounts of water. Tissue can spring back after being compressed. • Avascular and no nerve supply. Heals slowly. • Perichondrium. Dense irregular connective tissue that surrounds cartilage. Fibroblasts of perichondrium can differentiate into chondroblasts. • Types of cartilage – Hyaline – Fibrocartilage – Elastic 4-65 Hyaline Cartilage Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.10 Supporting Connective Tissue: Cartilage

(a) Hyaline Cartilage

Structure: Collagen fibers are small and evenly Function: Allows the growth of long Location: Growing long bones, cartilage rings of the dispersed in the matrix, making the matrix appear bones; provides rigidity with some respiratory system, costal cartilage of ribs, nasal cartilages, transparent; the cartilage cells, or chondrocytes, flexibility in the trachea, bronchi, ribs, articulating surface of bones, embryonic skeleton are found in spaces, or lacunae, within the firm and nose; forms rugged, smooth, yet but flexible matrix somewhat flexible articulating surfaces; forms the embryonic skeleton

Bone

Hyaline cartilage

Chondrocyte in alacuna

Nucleus

Matrix

LM 240x

© Carolina Biological Supply/Phototake.com • Structure: large amount of collagen fibers evenly distributed in proteoglycan matrix. Smooth surface in articulations • Locations: – Found in areas for strong support and some flexibility: rib cage, trachea, and bronchi – In embryo forms most of skeleton 4-66 – Involved in growth that increases bone length Chondrocytes Hyaline Cartilage Lacunae

Extracellular matrix Nuclei of chondrocytes Perichondrium Fibrocartilage • Structure: thick collagen fibers distributed in proteoglycan matrix; slightly compressible and very tough • Locations: found in areas of body where a great deal of pressure is applied to joints – Knee, jaw, between vertebrae

TABLE 4.10 Supporting Connective Tissue: Cartilage

(b) Fibrocartilage

Structure: Collagen fibers similar to those in Function: Somewhat flexible and Location: Intervertebral disks, symphysis pubis hyaline cartilage; the fibers are more numerous capable of withstanding considerable pressure; articular disks (e.g., knee and temporomandibular than in other cartilages and are arranged in connects structures subjected to great pressure [jaw] joints) thick bundles

Chondrocyte in lacuna Nucleus

Inter vertebral disk Collagen fibers in matrix

LM 240x

Collagen fibers Nuclei of chondrocytes Ground substance Elastic Cartilage • Structure: elastic and collagen fibers embedded in proteoglycans. Rigid but elastic properties • Locations: external ears and epiglottis

Structure: Similar to hyaline cartilage, but Function: Provides rigidity with even more Location: External ears, epiglottis, auditory tubes matrix also contains elastic fibers flexibility than hyaline cartilage because elastic fibers return to their original shape after being stretched

Elastic fibers in matrix

Chondrocytes in lacunae

Nucleus

LM 240x

4-70 Elastic Cartilage Chondrocytes Elastic fibers

Ground substance Lacunae

Nuclei of chondrocytes Perichondrium Supporting Connective Tissue: Bone

• Hard connective tissue composed of living cells (osteocytes) and mineralized matrix • Matrix: gives strength and rigidity; allows bone to support and protect other tissues and organs – Organic: collagen fibers

– Inorganic: hydroxyapatite (Ca plus PO4) • Osteocytes located in lacunae • Types – Spongy bone – Compact bone

4-72 Spongy Bone

Marrow cavity Trabeculae Bone

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.11 Supporting Connective Tissue: Bones (a) Spongy Bone • Spongy bone: trabeculae Structure: Latticelike network of scaffolding Function: Acts as scaffolding to provide Location: In the interior of the bones of characterized by trabeculae with large spaces strength and support without the greater the skull, vertebrae, sternum, and pelvis; between them filled with hemopoietic tissue; weight of compact bone in the ends of the long bones the osteocytes, or bone cells, are located of bone with spaces within lacunae in the trabeculae

Osteoblast between. Looks like a nuclei Spongy bone

Bone trabecula sponge. Found inside Bone marrow Osteocyte nucleus bones. Matrix

LM 240x • Compact bone: arranged (b) Compact Bone in concentric circle layers Structure: Hard, bony matrix predominates; Function: Provides great strength and support; Location: Outer portions of all bones, many osteocytes (not seen in this bone preparation) forms a solid outer shell on bones that keeps the shafts of long bones are located within lacunae that are distributed them from being easily broken or punctured in a circular fashion around the central canals; small passageways connect adjacent lacunae around a central canal that

Lacuna contains a blood vessel.

Central canal Found on periphery of bones. Matrix Compact bone organized into lamellae

LM 240x

4-74 Compact Osteon Interstitial lamellae Bone

Cement line

Central Canal Osteocytes in lacuna Fluid Connective Tissue: Blood

• Matrix: plasma – Liquid and lacks fibers. – Matrix formed by other tissues, unlike other types of connective tissue. – Moves through vessels, but both fluid and cells can move in/out of the vessels. • Formed elements: red cells, white cells, and platelets Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

TABLE 4.12 Fluid Connective Tissue: Blood and Hemopoietic Tissue

• Hemopoietic tissue (a) Blood

Structure: Blood cells and a fluid Function: Transports oxygen, carbon dioxide, Location: Within the blood vessels; white blood matrix hormones, nutrients, waste products, and other cells frequently leave the blood vessels and enter substances; protects the body from infections and the interstitial spaces – Forms blood cells is involved in temperature regulation – Two types of bone marrow Red blood cell

White White blood blood cell • Yellow cells • Red Red blood cells

LM 400x

4-76 Fluid Connective Tissue: Hemopoietic Tissue • Forms blood cells • Found in bone marrow • Types of bone marrow – Red: hemopoietic tissue surrounded by a framework of reticular fibers. Produces red and white cells – Yellow: yellow adipose tissue • As children grow, yellow marrow replaces much of red marrow.

TABLE 4.12 Fluid Connective Tissue: Blood and Hemopoietic Tissue

(b) Bone Marrow

Structure: Reticular framework Function: Produces new blood cells (red marrow); Location: Within marrow cavities of bone; two types: with numerous blood-forming cells stores lipids (yellow marrow) (1) red marrow (hemopoietic, or blood-forming, (red marrow) tissue) in the ends of long bones and in short, flat, and irregularly shaped bones and (2) yellow marrow, mostly adipose tissue, in the shafts of long bones

Cells destined to become red blood cells Spongy bone (with red m arrow)

Marrow cavity (with yellow marrow)

Fat

Nuclei

Platelets

Neutrophils 4.5 Muscle Tissue • Characteristics – Contracts or shortens with force – Moves entire body and pumps blood • Types – Skeletal: most attached to skeleton, but some attached to other types of connective tissue. Striated and voluntary. – Cardiac: muscle of the heart. Striated and involuntary. – Smooth: muscle associated with tubular structures and with the skin. Nonstriated and involuntary.

TABLE 4.13 Comparison of Muscle Types

Skeletal Muscle Cardiac Muscle Smooth Muscle

Location Attached to bones In the heart In the walls of hollow organs, blood vessels, eyes, glands, skin

Cell Shape Very long, cylindrical cells (1–4 cm and may Cylindrical cells that branch Spindle-shaped cells (15–200 µm in extend the entire length of the muscle, (100–500 µm in length, 12–20 length, 5–8 µm in diameter) 10–100 µm in diameter) µm in diameter)

Nucleus Multinucleated, peripherally located Single, centrally located Single, centrally located

Striations Yes Yes No

Control Voluntary(conscious) Involuntary(unconscious) Involuntary (unconscious)

Ability to Contract No Yes Yes Spontaneously

Function Moves the body Provides the major force for moving Moves food through the digestive blood through the blood vessels tract, empties the urinary bladder, regulates blood vessel diameter, changes pupil size, contracts many gland ducts, moves hair, performs many other functions

Special Features None Branching fibers, intercalated Gap junctions disks containing gap junctions joining the cells to each other

4-80 Skeletal Muscle

TABLE 4.14 Muscle Tissue

(a) Skeletal Muscle

Structure: Skeletal muscle cells or Function: Moves the body; is under Location: Attached to bone or other fibers appear striated (banded); cells voluntary (conscious) control connective tissue are large, long, and cylindrical, with many nuclei located at the periphery Muscle

Nucleus (near periphery of cell)

Skeletal muscle fiber

Striations LM 800x

A band

TABLE 4.14 Muscle Tissue—Continued (b) Cardiac Muscle

Structure: Cardiac muscle cells are Function: Pumps the blood; is under Location: In the heart cylindrical and striated and have a involuntary (unconscious) control single, centrally located nucleus; they are branched and connected to one another by intercalated disks, which contain gap junctions

Nucleus (central)

Cardiac muscle cell

Intercalated disks (special junctions between cells )

Striations

LM 800x

4-83 Cardiac Muscle

Branched cardiac cell Intercalated disc Nuclei of cardiac cell Smooth Muscle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TABLE 4.14 Muscle Tissue—Continued

Structure: Smooth muscle cells are Function: Regulates the size of Location: In hollow organs, such tapered at each end, are not striated, organs, forces fluid through tubes, as the stomach and small and and have a single nucleus controls the amount of light entering large intestines Wall of stomach the eye, and produces “goose flesh” Wall of colon in the skin; is under involuntary (unconscious) control Wall of small intestine

Nucleus

Smooth muscle cell LM 500x

Smooth muscle fiber

Transverse smooth muscle fiber Smooth Muscle High Magnification Smooth muscle fiber

Nuclei of smooth muscle fiber 4.6 Nervous Tissue: Neurons • Neurons or nerve cells have the ability to produce action potentials – Parts: • Cell body: contains nucleus • Axon: cell process; conducts impulses away from cell body; usually only one per neuron • Dendrite: cell process; receive impulses from other neurons; can be many per neuron – Types: • Multipolar, bipolar, and unipolar

4-88 Nervous Tissue Neuron Nucleus of neuron

Nucleolus of neuron

Dendrites

Nissl substance

Axon Nuclei of glial cells Neurons

(a) Multipolar Neuron

Structure: The neuron consists of Function: Neurons transmit information Location: In the brain, dendrites, a cell body, and a long in the form of action potentials, spinal cord, ganglia Brain axon; neuroglia, or support cells, store “information,” and integrate and surround the neurons evaluate data; neuroglia support, protect, and form specialized sheaths Spinal around axons cord Spinal nerves

Dendrite

Cell body of neuron

Nucleus of neuron

Nuclei of neuroglia cells

Neuroglia cells

LM 240x Axon

(b) Pseudo-Unipolar Neuron

Structure: The neuron consists of a cell Function: Conducts action potentials Location: In ganglia outside the body with one axon from the periphery to the brain or spinal brain and spinal cord cord

Nuclei of neuroglia

Cell body of neuron

Nucleus of neuron

Branches of axon (not visible in photomicrograph) LM 240x 4-90

Nuclei of brain, spinal cord and neuroglia

nerves Cell body of neuron

• Nourish, protect, and Nucleus of neuron insulate neurons

LM 240x

Respiratory – Line cavities that open to the Digestive outside of body – Secrete mucus

(b) Serous membranes – Contains epithelium with goblet

Pleural cells, basement membrane, lamina Peritoneal propria (sometimes with smooth muscle) – Found in respiratory, digestive, urinary and reproductive systems. • Serous. simple squamous epithelium called mesothelium, basement

(c) Synovial membrane membrane, thin layer of loose C.T. – Line cavities not open to exterior • Pericardial, pleural, peritoneal • Synovial – Line freely movable joints – Produce fluid rich in hyaluronic acid

4-92 4.8 Tissue Damage and Inflammation • Responds to tissue damage or with an immune response • Manifestations – Redness, heat, swelling, pain, disturbed function • Chemical Mediators – Include histamine, kinins, prostaglandins, leukotrienes – Stimulate pain receptor and increase blood vessel permeability as well movement of WBCs to affected area.

Splinter Bacteria introduced

1 A splinter in the skin causes damage and introduces bacteria. Chemical mediators of inflammation are released or activated in 1 Epidermis injured tissues and adjacent blood vessels . Some blood vessels rupture, causing bleeding.

2 Chemical mediators cause capillaries to dilate and the skin to become red. Chemical 2 Dermis mediators also increase capillary permeability, and fluid leaves the capillaries, producing swelling (arrows). Blood vessel

Bacteria proliferating

3 White blood cells (e.g., neutrophils) leave the dilated blood vessels and move to the site of bacterial infection, where they begin to 3 phagocytize bacteria and other debris.

Neutrophil phagocytizing bacteria Neutrophil 4-94 migrating through blood vessel wall 4.9 Tissue Repair • Substitution of dead/damaged cells by viable/functional cells • Types of cells – Labile: capable of mitosis through life. skin, mucous membranes, hemopoietic tissue, lymphatic tissue – Stable: no mitosis after growth ends, but can divide after injury. Liver, pancreas, endocrine cells – Permanent: if killed, replaced by a different type of cell. Limited regenerative ability. nervous, skeletal and cardiac muscle

4-95 Skin Repair • Primary union: Edges of wound are close together – Wound fills with blood – Clot forms: fibrin threads start to contract; pull edges together – Scab – Inflammatory response; pus forms as white cells die – Granulation tissue. Replaces clot, delicate C.T. composed of fibroblasts, collagen fibers, capillaries – Scar. Formed from granulation tissue. Tissue turns from red to white as capillaries are forced out. • Secondary union: Edges of wound are not closed; greater chance of infection – Clot may not close gap – Inflammatory response greater – Wound contraction occurs leading to greater scarring 4-96 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. New epidermis Scab growing into wound Blood clot

1 Epidermis 2

Blood vessel

Dermis

Subcutaneous fat

Neutrophils migrating to wound site Fibroblasts migrating to wound site 1 Fresh wound cuts through the epithelium (epidermis) 2 Approximately 1 week after the injury, a scab is present, and underlying connective tissue (dermis), and a clot and epithelium (new epidermis) is growing into the wound. forms.

Freshly healed New epidermis epidermis Scab

Epidermis

Subcutaneous fat

Granulation tissue Granulation tissue being (fibroblasts replaced with new proliferating) connective tissue 3 Approximately 2 weeks after the injury, the epithelium 4 Approximately 1 month after the injury, the wound has has grown completely into the wound, and fibroblasts completely closed, the scab has been sloughed, and the 4-97 have formed granulation tissue. granulation tissue is being replaced by new connective tissue. 4.10 Effects of Aging on Tissues • Cells divide more slowly • Collagen fibers become more irregular in structure, though they may increase in number – Tendons and ligaments become less flexible and more fragile • Elastic fibers fragment, bind to calcium ions, and become less elastic – Arterial walls and elastic ligaments become less elastic • Changes in collagen and elastin result in – Atherosclerosis and reduced blood supply to tissues – Wrinkling of the skin – Increased tendency for bones to break • Rate of blood cell synthesis declines in the elderly

• Injuries don’t heal as readily 4-98