A&P 4: Tissues

a group of cells found together in the body

tissue

how does the structure of a tissue impact its function

the cells in a tissue are arranged in an orderly pattern that achieves the tissue’s functions

four broad categories of tissues:

epithelial, connective, muscle, and nervous

the microscopic study of tissue appearance, organization, and function

histology

this type of tissue refers to the sheets of cells that cover exterior surfaces of the body, line internal cavities and passageways, and form certain glands

epithelial tissue/epithelium

this type of tissue binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body

connective tissue

this type of tissue is excitable; it responds to stimulation and contracts to provide movement

muscle tissue

three major types of muscle tissue

skeletal (voluntary muscle), smooth muscle, and cardiac muscle

this type of tissue is also excitable; it allows the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body

nervous tissue

types/locations of nervous tissue

brain, spinal cord, nerves

types/locations of epithelial tissue

lining of the GI tract organs and other hollow organs; skin surface (epidermis)

types/locations of connective tissue

fat and other soft padding tissue, bone, tendon

three major germ layers established in the embryonic cells from which all tissues and organs eventually form

ectoderm, mesoderm, and endoderm

this germ layer gives rise to skin cells, neurons, and pigment cells

ectoderm

this germ layer gives rise to cardiac muscle, skeletal muscle, tubule cell of kidney, red blood cells, and smooth muscle

mesoderm

this germ layer gives rise to lung cells, thyroid cells, and pancreatic cells

endoderm

which germ layer(s) does epithelial tissue originate from

all three

which germ layer(s) does nervous tissue derive from

primarily the ectoderm

which germ layer(s) does muscle tissue derive from

mesoderm

a thin layer or sheet of cells that covers the outside of the body, the organs, internal passageways that lead to the exterior of the body, and the lining of the moveable joint cavities

tissue membrane

two basic types of tissue membranes:

connective tissue and epithelial membranes

which tissue membranes fall under the connective tissue membrane category

synovial membranes

which tissue membranes fall under the epithelial membrane category

mucous membranes, serous membranes, and the cutaneous membrane

this tissue membrane is formed solely from connective tissue

connective tissue membrane

these tissue membranes encapsulate organs and line our moveable joints

connective tissue membranes

a type of connective tissue membrane that lines the cavity of a freely moveable joint

synovial membrane

examples of synovial membranes

membranes surrounding the joints of the shoulder, elbow, and knee

briefly describe how synovial membranes work to protect joints

fibroblasts in the inner layer of the synovial membrane release hyaluronan into the joint cavity, which effectively traps water to form synovial fluid, which is a natural lubricant that enables the bones of a joint to move freely against one another without much friction

this tissue membrane is composed of epithelium attached to a layer of connective tissue

epithelial membrane

give an example of an epithelial membrane

skin

these epithelial membranes line the body cavities and hollow passageways that open to the external environment, and include the digestive, respiratory, excretory, and reproductive tracts

mucous membrane

what lines the epithelial layer

mucus

the underlying connective tissue that helps support the fragile epithelial layer

lamina propria

an epithelial membrane composed of mesodermally derived epithelium called the mesothelium that is supported by connective tissue

serous membrane

these membranes line the coelomic cavities of the body—those cavities that do not open to the outside—and cover the organs located within those cavities

serous membrane

describe how serous membranes reduce abrasion and friction between organs

the cells of the thin squamous mesothelium secretes serous fluid

four serous membranes (three of which line the thoracic cavity):

two pleura that cover the lungs, the pericardium that covers the heart, and the peritoneum that covers and suspends abdominal organs

a stratified squamous epithelial membrane resting on top of connective tissue

cutaneous membrane/the skin

describe how the cutaneous membrane helps protect the body from desiccation and pathogens

the apical surface is exposed to the external environment and is covered with dead, keratinized cells

the type of epithelium that lines hollow organs and body cavities not connected to the exterior of the body

endothelium

what are areas of the body other than skin that are exposed to the outside

airways, digestive tract, urinary and reproductive systems

from which embryonic germ layer did the epithelia lining the skin, parts of the mouth and nose, and the anus develop

ectoderm

from which embryonic germ layer did cells lining the airways and most of the digestive system originate

endoderm

from which embryonic germ layer did the epithelium lining vessels in the lymphatic and cardiovascular system (the endothelium) derive

mesoderm

list some shared structural and functional features of all epithelia

highly cellular; cell junctions; polarity between apical and basal surface; basal lamina; reticular lamina; basement membrane; nearly completely avascular

specialized intercellular connection between adjoining cells and their cell membranes

cell junction

exposed surface of the epithelial cell

apical surface

the surface of the epithelial cell close to the underlying body structures

basal surface

a mixture of glycoproteins and collagen that provides an attachment site for the epithelium and separates it from underlying connective tissue

basal lamina

the basal lamina attaches to this, which is secreted by the underlying connective tissue and forms a basement membrane

reticular lamina

helps hold everything together within the epithelium

basement membrane

what does it mean for epithelial tissues to be almost completely avascular

no blood vessels cross the basement membrane to enter the tissue and nutrients must come by diffusion or absorption from underlying tissues or the surface

________ tissues provide the body’s first line of protection from physical, chemical, and biological wear and tear

epithelial

how are epithelial cells typically characterized

by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces

microscopic extensions of the apical cell membrane that are supported by microtubules; beat in unison and move fluids as well as trapped particles

cilia

function of ciliated epithelium lining the ventricles of the brain

helps circulate the cerebrospinal fluid

the ciliated epithelium of your airway forms a mucociliary escalator that sweeps particles of dust and pathogens trapped in the secreted mucous toward…

the throat

true or false: epithelia cells are closely connected and not separated by intracellular material

true

three types of cell junctions:

tight junctions, anchoring junctions, and gap junctions

this cell junction separates the cells into apical and basal compartments; there is no extracellular space between adjacent epithelial cells and the movement of substances between cells is blocked; enables the epithelia to act as selective barriers

tight junction

this cell junction helps stabilize epithelial tissues; they are common on the lateral and basal surfaces of cells where they provide strong and flexible connections

anchoring junctions

three types of anchoring junctions:

desmosomes, hemidesmosomes, and adherens

this type of anchoring junction occurs in patches on the membranes of cells; the patches are structural proteins on the inner surface of the cell’s membrane and the adhesion molecule, cadherin, is embedded in them and projects through the membrane to link with adjacent cells; important for holding cells together

desmosomes

this type of anchoring junction looks like half a desmosome; it links cells to the extracellular matrix and includes the adhesion protein called integrins instead of cadherins

hemidesmosomes

this type of anchoring junction uses either cadherins or integrins depending on whether they are linking to other cells or matrix; characterized by the presence of contractile protein actin which can connect isolated patches or form a belt-like structure inside the cell; influence the shape and folding of the epithelial tissue

adherens junctions

this type of junction forms and intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between cells; allow electrical and metabolic coupling of adjacent cells, which coordinates function in large groups of cells

gap junction

how are epithelial tissues classified

according to the shape of the cells and number of the cell layers formed

flattened and thin epithelial cells

squamous

boxy, as wide as it is tall, epithelial cells

cuboidal

rectangular, taller than it is wide, epithelial cells

columnar

the number of cell layers in the epithelial tissue is one; every cell rests on the basal lamina

simple epithelium

the number of cell layers in the epithelial tissue is more than one; only the basal layer of cells rests on the basal lamina

stratified epithelium

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

pseudostratified epithelium

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

transitional epithelium

the cells in _______ epithelium have the appearance of thin scales; the nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell

simple squamous

this type of epithelium is present where rapid passage of chemical compounds is observed because of the thinness of the cell

simple squamous epithelium

examples of simple squamous epithelial tissue in the body

endothelium, mesothelium, alveoli of lungs, segments of kidney tubules, and lining of capillaries

a simple squamous epithelium that forms the surface layer of the serous membrane that lines the body cavities and internal organs; provides smooth and protective surface

mesothelium

the nucleus of this type of epithelial cell appears round and is generally located near the center of the cell

simple cuboidal epithelium

this type of epithelium is active in secretion and absorption of molecules

simple cuboidal

examples of simple cuboidal epithelia

lining of the kidney tubules and ducts of glands

the nucleus of this type of epithelial cell tends to be elongated and located in the basal end of the cell

simple columnar

examples of simple columnar epithelium

lining of some sections of the digestive system and parts of the female reproductive tract

simple columnar epithelium is active in the ________ of molecules

secretion and absorption

this type of epithelium is composed of simple columnar epithelial cells with cilia on their apical surfaces

ciliated columnar epithelium

examples of ciliated columnar epithelia

lining of the fallopian tubes and parts of the respiratory system

a type of epithelium that appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells

pseudostratified columnar epithelium

examples of pseudostratified columnar epithelium

respiratory tract, some ciliated

why are simple and pseudostratified columnar epithelia “heterogenous” epithelia

they include additional types of cells interspersed among the epithelial cells

a mucous-secreting unicellular “gland” interspersed between the columnar epithelial cells of mucous membranes

goblet cell

how are stratified epithelia named

based on the shape of the most apical layer of cells

the most common type of stratified epithelium in the human body; the apical cells are squamous, whereas the basal layer contains either columnar or cuboidal cells; the top layer may be covered with dead cells filled with keratin

stratified squamous epithelium

what is an example of a dry, keratinized, stratified squamous epithelium

mammalian skin

what is an example of an unkeratinized, stratified squamous epithelium

the lining of the mouth cavity

these epithelia can be found in certain glands and ducts, but are uncommon in the human body

stratified cuboidal and stratified columnar

a specific kind of stratified epithelium that gradually changes in the shape of its apical cells

transitional epithelium

where are transitional epithelia found

only in the urinary system, specifically the ureters and urinary bladder

what do transitional epithelia look like when the bladder is empty

convoluted and cuboidal apical cells with convex, umbrella shaped, apical surfaces

what does the transitional epithelia look like when the bladder is filled with urine

apical cells are squamous; thicker and more multi-layered more stretched out and less stratified

a structure made up of one or more cells modified to synthesize and secrete chemical substances

gland