Human A&P Chapter 5

Epithelial Tissue

Epithelial Tissue

Tissue composed of layers of closely spaced cells that cover organ surfaces, form glands, and serve for protection, secretion, and absorption

Connective Tissue

Tissue with usually more matrix than cell volume, often specialized to support and protect organs and to bind other tissues and organs to each other

Nervous Tissue

Tissue containing excitable cells specialized for rapid transmission of coded information to other cells

Muscular Tissue

Tissue composed of elongated, excitable muscle cells specialized for contraction

Matrix

The extracellular material of a tissue, composed of fibers and ground Substance

Tissue

A group of similar cells and cell products that arise from the same region of the embryo and work together to perform a specialized structural or physiological role in an organ

Epithelium

Covers the body surface (skin), lines body cavities, forms the external and internal linings of many organs, and constitutes most gland tissue. They are avascular (without blood vessels)

Basement Membrane

Layer between an epithelium and underlying connective tissue

Simple Epithelium

Every cell is anchored to the basement membrane

Stratified Epithelium

Some cells rest on top of other cells and don't contact the basement membrane

Simple Squamous Epithelium

Single layer of thin cells, shaped like fried eggs with bulge where nucleus is located; nucleus flattened in the plane of the cell

Location of simple squamous epithelium

Air Sacs (alveoli) of lungs; glomerular capsules of kidneys; some kidney tubules; inner lining of heart & blood vessels: serous membranes of stomach, intestines, and some other viscera; surface mesothelium of pleura, pericardium, peritoneum, and mesenteries

Function of simple squamous epithelium

Allows rapid diffusion or transport of substances through membrane; secretes lubricating serous fluid.

Simple Cuboidal Epithelium

Single layer of square or round cells; in glands, cells often pyramidal and arranged like segments of an orange around a central space; spherical, centrally placed nuclei

Location of simple cuboidal epithelium

Liver, thyroid, mammary, salivary, and other glands; most kidney tubules; bronchioles

Function of simple cuboidal epithelium

Absorption and secretion; production of protective mucous coat; movement of respiratory mucus

Simple Columnar Epithelium

Single layer of tall, narrow cells; oval or sausage shaped nuclei, vertically oriented, usually in basal half of cell; often shows a brush border of microvilli; ciliated in some organs; may possess goblet cells

Location of simple columnar epithelium

Inner lining of stomach, intestines, gallbladder, uterus, and uterine tubes; some kidney tubules

Function of simple columnar epithelium

Absorption; secretion of mucus and other products; movement of egg and embryo in uterine tube

Pseudostratified Columnar Epithelium

Looks multilayered; some cells do not reach free surface, but all cells reach basement membrane; nuclei at several levels in deeper half of epithelium; often with goblet cells; often ciliated

Location of pseudostratified columnar epithelium

Respiratory tract from nasal cavity to bronchi; Portion of male urethra

Function of pseudostratified columnar epithelium

Secretes and Propels mucus

Stratified Squamous Epithelium (Keratinized)

Multiple cell layers with cells becoming increasingly flat and scaly toward surface; surface covered with a layer of compact dead cells without nuclei; basal cells may be cuboidal to columnar

Location of stratified squamous epithelium (keratinized)

Epidermis, palms and soles are especially heavily keratinized

Function of stratified squamous epithelium (keratinized)

Resists abrasion and penetration by pathogenic organisms; retards water loss through skin

Stratified Squamous Epithelium (Nonkeratinized)

Same as keratinized epithelium but without the surface layer of dead cells

Location of stratified squamous epithelium (nonkeratinized)

Tongue, oral mucosa, esophagus, anal canal, vagina

Function of stratified squamous epithelium (nonkeratinized)

Resists abrasion and penetration by pathogenic organisms

Stratified Cuboidal Epithelium

Two or more layers of cells; surface cells square or round

Location of stratified cuboidal epithelium

Sweat gland ducts; egg producing vesicles (follicles) of ovaries; sperm

Function of stratified cuboidal epithelium

Contributes to sweat secretion; secretes ovarian hormones; produces sperm

Transitional Epithelium

Multilayered; surface cells change from round to flat when stretched

Location of transitional epithelium

Urinary tract (part of kidney, ureter, bladder, part of urethra)

Function of transitional epithelium

Stretches to allow filling of urinary tract; protects underlying tissues from osmotic damage by urine

Connective tissue

Generally occupy less space than the extracellular matrix, usually their cells are not in direct contact with each other

Fibroblasts

Produce the fibers and ground substances that form the matrix

Fibrous connective tissue, adipose tissue, supportive connective tissues, and fluid connective tissue

Four broad categories of connective tissue

Areolar Tissue

Loose arrangement of collagenous and elastic fibers, scattered cells of various types; abundant ground substance, numerous blood vessels

Location of areolar tissue

Underlying nearly all epithelia; surrounding blood vessels, nerves, esophagus, and trachea; fascia between muscles; mesenteries, visceral layers of pericardium and pleura

Function of areolar tissue

Loosely binds epithelia to deeper tissues; allows passage of nerves and blood vessels through other tissues; provides an arena for immune defense; blood vessels provide nutrients and waste removal for overlying epithelia

Reticular Tissue

Loose network of reticular fibers and cells, infiltrated with numerous leukocytes, especially lymphocytes

Location of reticular tissue

Lymph nodes, spleen, thymus, bone marrow

Function of reticular tissue

Forms supportive stroma (framework) for lymphoid organs

Dense Regular Connective Tissue

Densely packed, parallel, often wavy collagen fibers; slender fibroblast nuclei compressed between collagen bundles; small amount of open space (ground substance); scarcity of blood vessels

Location of dense regular connective tissue

Tendons and ligaments.

Function of dense regular connective tissue

Ligaments tightly bind bones together and resist stress; tendons attach muscle to bone and transfer muscular tension to bones

Dense Irregular Connective Tissue

Densely packed collagen fibers running in random directions; not a lot of open space (ground substance); few visible cells; scarcity of blood vessels

Location of dense irregular connective tissue

Deeper portion of dermis of skin; capsules around viscera such as liver, kidney, spleen; fibrous sheaths around cartilages and bones

Function of dense irregular connective tissue

Withstands stresses applied in unpredictable directions; imparts durability to tissues.

Adipose Tissue

Dominated by adipocytes, large, empty looking cells with thin margins; tissue sections often very pale because of scarcity of stained cytoplasm; adipocytes shrunken; nucleus pressed against plasma membrane; blood vessels present

Location of adipose tissue

Subcutaneous fat beneath skin; breast; heart surface; mesenteries; surrounding organs such as kidneys and eyes

Function of adipose tissue

Energy Storage; thermal insulation; heat production by brown fat; protective cushion for some organs; filling space, shaping body

Hyaline Cartilage

Clear, glassy matrix, often stained light blue or pink in tissue sections; fine, dispersed collagen fibers, not usually visible; chondrocytes enclosed in lacunae, often in small clusters of three or four cells; usually covered by perichondrium.

Location of hyaline cartilage

Over the ends of bones at movable joints; supportive rings and plates around trachea and bronchi; boxlike enclosure around larynx; much of the fetal skeleton; and a coastal cartilage attaches the end of a rib to the breastbone

Function of hyaline cartilage

Eases joint movements; holds airway open during respiration; moves vocal cords during speech; a precursor of bone in the fetal skeleton and the growth zones of long bones of children

Elastic Cartilage

Elastic fibers form weblike mesh amid lacunae, always covered by perichondrium.

Location of elastic cartilage

External ear; epiglottis

Function of elastic cartilage

Provides flexible, elastic support

Fibrocartilage

Parallel collagen fibers similar to those of tendon; rows of chondrocytes in lacunae between collagen fibers; never has a perichondrium

Location of fibrocartilage

Pubic Symphysis, intervertebral discs, menisci, in knee joint

Function of fibrocartilage

Resist compression and absorbs shock in some joints; often a transitional tissue between dense connective tissue and hyaline cartilage

Bone

Calcified matrix arranged in concentric lamellae around central canals; osteocytes in lacunae between adjacent lamellae; lacunae interconnected by delicate canaliculi

Location of bone

Skeleton

Function of bones

Physical support of body; leverage for muscle action; protective enclosure of viscera; reservoir of calcium and phosphorous

Blood

Erythrocytes appear as pale pink discs with light centers and no nuclei; leukocytes are slightly larger, are much fewer, and have variously shaped nuclei, usually stained violet; platelets are cell fragments with no nuclei, much smaller than erythrocytes

Location of blood

Contained in heart and blood vessels.

Function of blood

Transports gases, nutrients, wastes, chemical signals, and heat throughout the body; provides defense leukocytes; contains clotting agents to minimize bleeding; platelets secrete growth factors that promote tissue maintenance and repair

Collagen

The most abundant protein in the body, forming the fibers of many connective tissues in places such as the dermis, tendons, and bones

Reticular Fibers

Thin collagen fibers coated with glycoprotein. They form a spongelike framework for such organs as the spleen and lymph nodes and constitute part of the basement membranes underlying epithelia

Elastic Fibers

Thinner than collagenous fibers, and they branch and rejoin each other along their course. Made of a protein called elastin coated with a glycoprotein. Stretches and recoils like a rubber band

Collagenous Fibers

Fibers made of collagen that are tough, flexible, and resist stretching. Makes up tendons, ligaments, and deep layer of skin

Neurons (nerve cells), neuroglia (glial cells), dendrites (receives signals from other cells), neurosoma (cell body)

Cell types that compose nervous tissue

Nervous Tissue

Most sections show a few large neurons, usually with rounded or stellate cell bodies and fibrous processes (axon and dendrites) extending from the cell bodies; neurons are surrounded by a greater number of much smaller glial cells, which lack dendrites and axons

Location of nervous tissue

Brain, Spinal Cord, nerves, ganglia.

Function of nervous tissue

Internal Communication

Skeletal Muscle

Long, threadlike, unbranched cells (fibers), relatively parallel in longitudinal tissue sections; striations; multiple nuclei per cell, near plasma membrane

Location of skeletal muscle

Mostly attached to bones but also in the tongue, esophagus, and encircling the lips, eyelids, urethra, and anus.

Function of skeletal muscle

Body movements, facial expressions, posture, breathing, speech, swallowing, control of urination and defecation, and assistance in childbirth; under voluntary control

Cardiac Muscle

Short Cells (Cardiomyocytes) with notched or slightly branched ends; less parallel appearance in tissue sections; striations; intercalated discs; one nucleus per cell, centrally located and often surrounded by a light zone

Location of cardiac muscle

Heart

Function of cardiac muscle

Pumping of blood; under involuntary control

Smooth Muscle

Short fusiform Cells overlapping each other; nonstriated; one nucleus per cell, centrally located

Location of smooth muscle

Usually found as Sheets of tissue in walls of blood vessels and viscera such as the digestive tract; also in the iris and associated and with hair follicles; involuntary Sphincters of urethra and anus

Function of smooth muscle

Swallowing; contractions of stomach and intestines; expulsion of feces and urine; labor contractions; control of blood pressure and flow; control of respiratory airflow; control of pupillary diameter; erection of hairs; under involuntary control

Cellular junctions

The connections between one cell and another

Tight Junction

A junction in which the plasma membranes of two adjacent cells come very close together and are linked by transmembrane cell. Prevents molecules from passing in between cells

Desmosomes

A patchlike intercellular junction that mechanically links two cells together; not continuous and can’t prevent substances from passing around them and going between the cells, but keep cells from pulling apart and enable a tissue to resist mechanical stress

Gap Junctions

A junction between two cells consisting of a pore surrounded by a ring of proteins in the plasma membrane of each cell; allows solutes to diffuse from the cytoplasm of one cell to the next.

Gland

A cell or organ that secretes substances for use elsewhere in the body or for elimination as waste. Composed mostly of epithelial tissue, but usually have a supportive connective tissue framework and capsule

Exocrine Glands

A gland that secretes its product into another organ or onto the body surface, usually by way of a duct, an epithelial tube that conveys their secretion to the surface

Endocrine Glands

A ductless gland that secretes hormones into the bloodstream

Simple Gland

Gland with a single unbranched duct.

Compound Gland

Gland with a branched duct.

Tubular Gland

Gland with the duct and secretory portion of uniform diameter

Acinar Gland

Gland with secretory vesicles that form a sac

Tubuloacinar Gland

Gland with secretory cells in both the tubular and acinar portions

Eccrine, apocrine, holocrine

Modes of secretion

Eccrine Glands

Pertaining to gland cells that release their products by means of exocytosis. Found all over the body, produce a more water substance (sweat)

Apocrine Glands

Pertaining to certain sweat glands with large lumens and relatively thick, aromatic secretions and to similar glands such as the mammary gland. Secretes proteins and fatty acids

Holocrine Glands

Gland in which cells accumulate a product and then the entire cell disintegrates