Tissues 1122

Tissues

groups of cells that

are similar in structure and

perform a common function

Epithelial Tissue

(Epithelium plural)

Sheets of cells that cover the body’s surfaces

or lines a body cavity, 2 types Covering and Lining & Glandular Epithelium

Epithelial Apical surface,

upper free side, is exposed to surface or

cavity

• Most apical surfaces are smooth, but some have

specialized fingerlike projections called microvilli

Epithelial Basal surface

ower attached side, faces inwards toward

body

• Attaches to basal lamina, an adhesive sheet that holds

basal surface of epithelial cells to underlying cells

Basement membrane

Between the epithelial tissue and CT

Epithelial Tissue is

Avascular, Innervated &

Regenerative

Simple

one layer

• Typically found at sites of

• Absorption

• Secretion

• Filtration

Stratified

multilayered or

stacked

• More common where

abrasion can occur

Simple squamous epithelium

Air sacs of lungs

• Blood vessels

• Lymphatic vessel

Simple Cuboidal

• Secretion & absorption

• Ducts of glands

• Kidney tubules

• Simple Columnar

• Digestive Tract has two distinct

modifications for

these functions

• Microvilli on apical surface (absorptive

cells)

• Tubular glands that secrete

mucus/intestinal juic

Pseudostratified Columnar Epithelium

• Many cells are ciliated

• Located mostly in upper respiratory tract,

ducts of large glands, and tubules in testes

Stratified squamous epithelium

Located in areas of high wear and tear

(example: skin)

• Keratinized cells found in skin;

nonkeratinized cells are found in moist

linings

Stratified cuboidal epithelium

Quite rare

• Found in some sweat and mammary glands

• Typically, only two cell layers thick

Stratified columnar epithelium

• Small amounts found in pharynx, in male

urethra, and lining some glandular ducts

• Only apical layer is columnar

Transitional epithelium

Forms lining of hollow urinary organs

• Found in bladder, ureters, and urethra

gland

one or more cells that produce and secrete a particular

substance, called a secretion

Endocrine

internally secreting (example: hormones)

Exocrine

externally secreting (example: sweat)

mucous cells and

goblet cells

unicellular cells that produce mucin

compound glands

have branched

ducts

tubular gland

secretory cells form a

duct,

alveolar glands

secretory

cells form sacs

Merocrine

most secrete products by

exocytosis as secretions are produced

(sweat, pancreas)

Holocrine

accumulate products within, then

rupture (sebaceous oil glands)

Connective tissue

the most abundant

and widely distributed tissue of the body

But connective tissue consists

largely of a…

nonliving extracellular

matrix (a protein-sugar mesh)

• Cells are suspended/embedded

in this matrix

• Separates the living cells of tissues

• Because of this CT can bear

weight, withstand A LOT of

tension, and endure abuse such

as trauma and abrasion

CT Vascularity

some CT is highly

vascularized, while

others are avascular

Ground

Substance

the unstructured gel-like material that fills the

space between cells and contains the fibers

• Acts as a medium through which solutes diffuse between blood

capillaries and cells

Collagen

CT fiber that is Strongest and most abundant type

• Tough; provides high tensile strength

Elastic fibers

CT fiber that has Networks of long, thin, elastin fibers that allow for stretch and recoil

Reticular

CT fiber that has Short, fine, highly branched collagenous fibers (different chemistry and form from

collagen fibers)

• Branching forms networks that offer more “give”

blast vs cyte

blast immature, cyte mature

CT Proper Loose:

Areolar Connective

Tissue

Functions:

• Supports and binds other tissues

• Holding body fluids

• Defending against infection

• Universal packing material between other

tissues

CT Proper Loose:

Adipose Tissue

Cells are called adipocytes, Functions in shock absorption,

insulation, and energy storage, has brown and white fat

CT Proper Loose:

Reticular

Fibroblast cells are called reticular

cells

• Reticular fibers form a mesh-like

stroma that acts as a support for

blood cells in lymph nodes,

spleen, and bone marrow

CT Proper Dense:

Regular

Example: tendons and ligaments

CT Proper Dense:

Irregular

Forms sheets rather than bundles

• Resists tension from many

directions

• Found in:

• Dermis

• Fibrous joint capsules

• Fibrous coverings of some

organs

CT Proper Dense:

Elastic CT

Some ligaments are very

elastic

• Example:

• Ligaments connecting

adjacent vertebrae must be

very elastic

• Also found in walls of many

large arteries

Cartilage

a strong, flexible connective tissue that cushions joints, reduces friction between bones, and gives shape to structures like the ears and nose, secreted from chondroblasts

(during growth) and chondrocytes, Avascular: receives nutrients from

membrane surrounding it

(perichondrium)

Hyaline Cartilage

Most abundant; “gristle”

• Found at tips of long bones, nose, trachea,

larynx, and cartilage of the ribs, tip of nose

Elastic Cartalige

Found in ears and epiglottis

Fibrocartilage

Strong, so found in areas such as

intervertebral discs and knee

Blood

Most atypical connective tissue

because it is fluid

• Consists of cells surrounded by

matrix (plasma)

Cutaneous membrane

• Skin

• Organ system consisting of stratified

squamous epithelia (epidermis) attached

the CT (dermis)

Mucous membrane

Line all the cavities that open to the

outside world

• Digestive, respiratory, urogenital

• All wet membranes bathed by secretions

Serous

• Line body cavities

• Have a visceral and parietal layer

Three Steps to tissue repair

• Inflammation

• Organization

• Regeneration

Organization

restores blood supply, begins as the blood

clot is replaced with granulation

tissue (new capillary-enriched

tissue – restores vascular supply)

apoptosis

n orderly, regulated form of programmed cell death