Tissues: Epithelial and Connective

Simple epithelia

contain a single layer of cells, with each cell attached to the basement membrane

Stratified epithelia

contain more than one layer of cell. The cells on the basal surface are attached to the basement membrane; those on the apical surface border an open space

Squamous cells

flat cells with flat, disc-shaped nuclei

Cuboidal cells

cube-shaped cells with spherical, centrally located nuclei

Columnar cells

taller than they are wide, like columns. The nuclei of columnar cells are located near the basal surface and are commonly oval in shape, elongated from top to bottom

simple squamous epithelium

function: allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae (linings of ventral body cavity)

location: kidney glomeruli; air sacs of lungs; lining of heart, blood vessels, and lymphatic vessels; serosaeis

simple cuboidal epithelium

function: secretion and absorption

location: kindey tubules; ducts and secretory portions of small glands; ovary surface

simple columnar epithelium

function: absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action

location: conciliated type lines most of the digestive tract (stomach to rectum), gallbladder, and excretory ducts of some glands; cilated variety lines small bronchi uterine tubes, and some regions of the uterus

pseudostratified columnar epithelium

function: secrete substances, particularly mucus; propulsion of mucus by ciliary action

location: ciliated variety lines the trachea and most of the upper respiratory tract; nonciliated type in males’ sperm-carrying ducts and ducts of large glands

stratified squamous epithelium

function: protects underlying tissues in areas subjected to abrasion

location: nonkerantinized type forms the most linings of the esophagus, mouth, and vagina; keratinized variety forms the epidermis of the skin, a dry epithelium

stratified cuboidal epithelium

function: protection

location: largest ducts of sweat glands, mammary glands, and salivary glands

stratified columnar epithelium

function: protection; secretion

location: rare in the body; small amounts in male urethra and in large ducts of some glands

transitional epithelium

function: stretched readily, permits stored urine to distend urinary organ

location: lines the ureters, bladder, and part of the urethra

endocrine glands

internal secretion; ductless glands; produce hormones

exocrine glands

external secretion; numerous; secrete their products onto body surfaces (skin) or into body cavities (such as the digestive tube)

unicellular exocrine glands

goblet cell; shaped like a goble; scattered within the epithelial lining of the intestines and respiratory tubes

multicellular exocrine glands

an epithelium-walled duct and secretory unit (secretory epithelium)

cell junctions

specialized protein structures the connect neighboring cells to each other or to the extracellular matrix

tight junctions

belt-like junctions that encircle the apical region epithelial cells, near the free surface

adhesive belt junctions

type of anchoring cell junction found just below the tight junctions in epithelial tissues

desmosomes

binding cells together tightly; an anchoring junction

gap junction

a tunnel-like junction that can occur anywhere along the lateral membranes of adjacent cells

basal lamina

sheets; thin, noncellular sheet consists of proteins secreted by the epithelial cells

basement membrane

a layer between an epithelium and the under lying connective tissue; consists of both a basal lamina and a network of reticular fibers.

microvilli

fingerlike extensions of the plasma membrane of apical epithelial cells

cilia

whiplike, highly motile extensions of the apical surface membranes of certain epithelial cells

basal body

centriole at the base of each cilium

flagellum

an extremely long, isolated cilium

loose connective tissue

1) Areolar

2) Adipose

3) Reticular

dense connective tissue

1) regular

2) irregular

3) elastic

cartilage

1) hyaline cartilage

2) elastic cartilage

3) fibrocartilage

bone tissue

1) compact bone

2) spongy bone

blood

blood cell formation and differentiation are quite complex (RBCs, WBCs, platelets)

extracellular matrix

cells of connective tissues are separated from one another by a large amount of extracellular material

ground substance

nonfiber part of the extracellular matrix of connective tissue

mesenchyme

another feature common to connective tissues is that they all originate from the embryonic tissue

connective tissue → embryonic → mesenchyme

function: gives rise to all other connective tissue

location: primarily in embryo

connective tissue → proper → loose → areolar

function: wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid

location: widely distributed under epithelia of body, e.g., forms laminated propria of mucous membranes; packages organs; surrounds capillaries

connective tissue → proper → loose → adipose

function: provides reserve food fuel; insulates against heat loss; supports and protects organs

location: under skin in subcutaneous tissue; around kidneys and eyeballs; within abdomen; in breasts

connective tissue → proper → loose → reticular

function: fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages

location: lymphoid organs (lymph nodes, bone marrow, and spleen)

connective tissue → proper → dense → irregular

function: withstands tension exerted in may directions; provides structural strength

location: fibrous capsules of organs and joints; dermis of the skin; m submucosa of digestive tract

connective tissue → proper → dense → regular

function: attaches muscles to bones or muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction

location: tendons, most ligaments, aponeuroses

connective tissue → proper → dense → elastic

function: allows tissue to recoil after stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration

location: walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes

connective tissue → cartilage → hyaline

function: supports and reinforces; serves as resilient cushion; resists compressive stress

location: forms most of the embryonic skeleton; covers the ends of long bones in join cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx

connective tissue → cartilage → elastic

function: maintains the shape of a structure while allowing great flexibility

location: supports the external ear (pinna); epiglottis

connective tissue → cartilage → fibrocartilage

function: tensile strength allows it to absorb compressive shock

location: intervertebral discs; pubic symphysis; disc of knee joint

connective tissue → bone

function: support and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis)

location: bones

connective tissue → blood

function: transport respiratory gases, nutrients, wastes, and other substances

location: contained within blood vessels

fibroblasts

fiber buds or fiber formers; make the protein subunits of fibers

chondroblast

cells that secrete the matrix; cartilage formers

osteoblasts

cells that secrete in bone; bone formers

adipose

cells, store nutrients

white blood cells (WBCs)

respond to and protect against infectious agents (neutrophils, lymphocytes, eosinophils)

macrophages

specialize in phagocytosis; engulf and devour a wide variety of foreign materials

mast cells

mediate inflammation and promote healing

collagen fibers

the strongest and most abundant type of fiber in the connective tissue

reticular fibers

bundles of special type of collagen fibril; network

elastic fibers

contain rubberlike protein → function like rubber bands

loose areolar connective tissue

1. supporting and binding other tissues

2. holding body fluids

3. defending the body against infection

4. storing nutrients as fat

interstitial fluid

the cells of the body are bathed in tissue fluid

adipose tissue

similar to areolar connective tissue in structure and function; nutrient-storing function is much greater

subcutaneous tissue

much of the body’s adipose tissue occurs in the layer beneath the skin

visceral fat

a specific type of adipose (fat) tissue located inside the abdominal cavity

brown adipose tissue

produces heat and is a nutrient consumer

reticular connective tissue

resembles areolar tissue → only fibers in its matrix are reticular fibers

dense connective tissue

contains more collagen than areolar connective tissue does

dense irregular connective tissue

similar to areolar tissue; collagen fibers are much thicker

dense regular connective tissue

run in the same direction, parallel to the direction of pull; crowded between the collagen fibers are rows of fibroblasts

ligaments

bands or sheets that bind bones to one another

fascia

a fibrous membrane that wraps around muscles, muscle groups, large vessels and nerves

elastic connective tissue

a high proportion of elastic fibers; recoil after stretching

cartilage

a firm but flexible tissue, occurs in several parts of the skeleton

chondrocyte

mature form of a cartilage cell

lacuna

little depression or cavity; in bone and cartilage, each lacuna is occupied by a cell

bone tissue

a tremendous ability to support and protect body structures

osteocytes

mature bone cells

• inhabit cavities:

  • lacunae

  • singular - lacuna

blood

the fluid in the blood vessels

cutaneous membranes

covers the body surface (skin)

mucous membranes (mucosae)

line body cavities that are open to the exterior

serous membranes (serosae)

line body cavities that are to the exterior

mesothelium

a serous membrane consists of simple squamous epithelium

serous fluid

lying on a thin layer of areolar connective tissue; filtrate of the blood in capillaries in the connective tissue