A&P Unit 3

Tissue

Group of similar cells and cell products working
together to perform a specific role in an organ

4 Primary Tissue Types

Epithelial Tissue, Connective Tissue, Muscular Tissue, Nervous Tissue

Matrix

Extracellular fluid filled with fibrous proteins and ground substance

Ground Substance

A thick, gel-like substance found in the matrix and contains water, gases, minerals, nutrients, wastes, hormones, and other chemicals

Cell Junction

A specialized intercellular connection between
the cell membranes of adjacent cells

Epithelial Tissue

Sheets of closely adhering cells one or more cells thick; cover body surfaces and line body cavities; make up most glands; is avascular; has both an apical and basal surface

Avascular

Does not contain blood vessels

Apical Surface

The surface of the epithelial cell that faces away
from the basement membrane and is exposed to the environment

Basal Surface

The surface of the epithelial cell facing and connected to the basement membrane

Functions of Epithelial Tissue

Protects deeper tissues from injury and infection; Produces and releases chemical secretions; Excretes wastes; Absorbs chemicals including nutrients; Selectively filters substances; Senses stimuli

Basement Membrane

Layer between epithelial tissue and underlying connective tissue; anchors epithelium to connective tissue; contains collagen, glycoproteins, reticular proteins, and other types of proteins

Simple Columnar Epithelium

Active in the absorption and secretion of molecules

Squamous Cells

Flattened and thinly shaped cells

Columnar Cells

Rectangular; taller than they are wide

Cuboidal Cells

Boxy; as wide as they are tall

Pseudostratified

Describes tissue with a single layer of
irregularly shaped cells that give the appearance of more than one layer

Transitional

Describes a form of specialized stratified epithelium in which the shape of the cells can vary

Simple Cuboidal Epithelium

Active in the absorption and secretion of molecules

Pseudostratified Columnar Epithelium

Stratified Cuboidal Epithelium

Can be found in certain glands or ducts

Urothelium

Specialized epithelial tissue found only in the urinary tract

Simple Squamous Epithelium

Permits rapid diffusion or transport of a substance

Keratinized Stratified Squamous Epithelium

Found in the epidermis, palms, and soles of feet; resists abrasion and penetration from pathogenic organisms; repels water loss through skin

Non-Keratinized Stratified Squamous Epithelium

Resists abrasion and penetration of pathogenic organisms; found in the tongue, esophagus, and vagina

Areolar Tissue

A type of loose fibrous connective tissue that contains collagen fibers, elastic fibers, and reticular fibers; serves as passageways for blood vessels; underlies epithelia; found in serous membranes and in between muscles

Reticular Tissue

A type of loose connective tissue; contains reticular fibers, fibroblasts, and leukocytes; forms the supportive framework of lymphatic organs; found in lymph nodes, spleen, thymus, and bone marrow

Dense Fibrous Regular Connective Tissue

Densely packed parallel collagen fibers; compressed fibroblast nuclei; elastic tissue forms waves; forms joints, tendons, and ligaments

Dense Fibrous Irregular Connective Tissue

Densely packed, randomly arranged collagen fibers; withstand unpredictable stresses; found in deep layers of the skin and capsules around organs

Adipose Tissue

Fat tissue; contains adipocytes, areolar tissue, reticular tissue, and blood capillaries; the body’s main energy reservoir

Adipocytes

Cells that produce adipose tissue

White Fat

The main type of fat in the body; provides thermal insulation, provides cushion for organs (eyeballs and kidneys), and contributes to body contours (female breasts and hips)

Brown Fat

A type of fat found only in fetuses, infants, and young children; functions as a heat-generating tissue; the color comes from mitochondrial enzymes and blood vessels

Hyaline Cartilage

Eases joint movement, holds airway open, moves vocal cords, growth of juvenile long bone; clear, glassy appearance; found in articular cartilage, costal cartilage, trachea, larynx, fetal skeleton

Elastic Cartilage

Cartilage containing an abundance of elastic fibers; provides flexible, elastic support; found in the external ear and epiglottis

Fibrocartilage

Cartilage containing large, coarse bundles of collagen fibers and fibroblasts; resists compression and absorbs shock; found in the pubic symphysis, menisci, and intervertebral discs

Structure of Skin

Goblet Cells

Mucus cells; not epithelial cells

Loose Areolar Tissue

Connects skin to muscle

Fibroblasts

Cells that make fibers; found in connective tissues

Chondroblasts

Cells that make cartilage and produce matrix (that will eventually trap them); found in cartilage tissue

Cartilage

Stiff, flexible connective tissue; forms surface of the nose and ears; avascular

Chondrocytes

Cartilage cells that are trapped in lacunae

Lacunae

Cavities that surround Chondrocytes, turning them into chondroblasts

Perichondrium

Sheath of dense irregular connective tissue that surrounds elastic and most hyaline cartilage (not articular cartilage)

Lateral Surface

The sidewall of a cell

Lumen

Internal cavity

Exfoliation

The death of stratified squamous epithelial daughter cells

Umbrella Cells

Domed surface cells of the Urothelium

Lipid Rafts

Dense patches of the thick phospholipid bilayer of the Urothelium

Uroplakins

Proteins embedded into the lipid rafts; protect the urothelium and are impermeable to urine

Functions of Connective Tissue

Binding of Organs, Support (bones); Physical Protection, Immune Protection, Movement, Storage (energy, phosphorus, and calcium), Heat Production (metabolism), and Transport (via blood)

Glycosaminoglycan (GAG)

Long polysaccharides composed of amino sugars and uronic acid; regulate water and electrolyte balance of tissue; attracts Na+ and K+ ions

Chondroitin Sulfate

Most common GAG; abundant in bone and blood vessels; gives cartilage its stiffness

Proteoglycan

Large molecule made of a bristle-like arrangement of GAGs surrounding a protein core; binds cells to extracellular materials and give tissue fluid a gel-like consistency

Macrophages

Large, phagocytic cells that wander through connective tissue where they engulf and destroy bacteria, dead cells, and foreign particles

White Blood Cells

Called leukocytes; travel through the blood stream and spend most of their time in connective tissue; attack bacteria and lymphocytes

Plasma Cells

Certain lymphocytes turn into these cells when they detect foreign agents; synthesize antibodies (disease-fighting proteins); seen in lymph nodes, intestine walls, and inflamed tissue

Fat Cells

Called adipocytes; appear in small clusters in some fibrous connective tissue; called adipose tissue when they dominate an area

Collagenous Fibers

Tough, flexible, and stretch-resistant; tendons, ligaments, and deep layers of the skin are mostly collagen

Collagen

Most abundant of the body’s proteins (25%)

Reticular Fibers

Thin collagen fibers coated with glycoprotein; form framework of spleen and lymph nodes

Elastic Fibers

Thinner than collagenous fibers; made of protein called elastin; allows stretch and recoil

Tight Junctions

Linkage between two adjacent cells by transmembrane cell-adhesion proteins; Seals off intercellular space making it difficult for substance to pass between cells

Desmosome

Patch that holds cells together (like a clothing snap); Keeps cells from pulling apart by resisting mechanical stress; Hook-like, J-shaped proteins arise from cytoskeleton; Anchor cytoskeleton to membrane plaque; Transmembrane proteins from each cell joined by cell adhesion protein

Gap Junction

Ions, nutrients, and other small solutes pass between cells

Functions of the Skin

Resistance to trauma and infection and other barrier functions; Vitamin D synthesis; Sensation; Thermoregulation; Nonverbal Communication

Keratin

A tough protein found in epidermal cells

Epidermis

Stratified squamous epithelium tissue; first layer of the skin; keratinized; typically thin

Dermis

Second layer of the skin; contains connective tissue

Hypodermis

Connective tissue layer below the dermis; is not a part of the skin

Thick Skin

Covers palms, soles of feet, and surfaces of the fingers/toes

Thin Skin

Covers the rest of the body where thick skin is not found

Dermcidin and Defensins

Defensive antimicrobial peptides in the skin

Acid Mantle

Protective acidic film of the skin

Tactile Disc

Tactile nerves and their nerve fibers

Keratinocytes

Cells that produce keratin; majority of epidermal cells

Stem Cells

Undifferentiated cells that give rise to keratinocytes; found only in the stratum basale

Melanocytes

Cells that produce melanin; are only found in the stratum basale but have branched processes that spread to keratinocytes to distribute melanin

Melanin

Pigment that shields DNA from ultraviolet radiation

Tactile Cells

Touch receptor cells associated with dermal nerve fibers in stratum basale

Dendritic Cells

Macrophages originating in bone marrow that guard against pathogens; found in stratum spinousum and granuolsum

Stratum Basale

A single layer of stem cells and keratinocytes resting on the basement membrane; stem cells divide and give rise to keratinocytes that replace dead cells on the surface

Stratum Spinosum

Several layers of keratinocytes joined together by tight junctions; contains dendritic cells; named for the appearance of cells after histological preparation

Stratum Granulosum

3-5 layers of flat keratinocytes; cells contain dark-staining keratohyalin granules

Stratum Lucidum

Thin, pale layer found only in thick skin; keratinocytes packed with clear protein called eleidin

Stratum Corneum

Several layers of dead, scaly, keratinized cells; resist abrasion, penetration, and water loss

Lamellar Granule

Lipid-filled granules

Gland

Cell or organ that secretes substances for use elsewhere in the body or releases them for elimination from the body

Excretion

Waste product; gets expelled from the cell/body

Secretion

A product useful to the body; gets released into the body/blood stream

Connective Tissue

A diverse, abundant type of tissue in which cells occupy less space than matrix; supports, protects, and connects organs

Dense Connective Tissue

Fibers fill spaces between cells; types vary in fiber orientation

Loose Connective Tissue

Much gel-like ground substance between cells; has many blood vessels

Exocrine Glands

Maintain their contact with the surface of epithelium by way of a duct; external (sweat/tear) or internal surfaces (pancreas/salvatory)

Endocrine Glands

Have no ducts; secrete hormones directly into blood

Hormones

Chemical messengers that stimulate cells elsewhere in the body

Mammary Glands

Produce milk for nursing mothers

Sweat Glands

Create and Secrete Waste

Sebaceous Glands

On the skin and hair follicles; secrete sebum

Eccrine Sweat Glands

Cover almost the entire body surface; secrete clear, non-oily sweat that helps regulate body temperature