Anatomy and Physiology: Epithelial Cells

what are epithelial cells?

cells that carry on the same function and work together to make tissue

what do epithelial cells make?

epithelial tissue

what is another word for epithelial tissue?

epithelium

what does the epithelial tissue make?

the lining, covering, and glandular tissue of the body

what does epithelial tissue cover?

the outside of the body which protects us from our surrounding environment

anything that enters or exits our body must pass through what?

the epithelial tissue

what are the functions of epithelium?

protection, absorption, filtration, and secretion

what does epithelium of the skin do?

protects us against bacterial and chemical damage

what does epithelium lining of the respiratory tract do?

contains cilia, which sweep dust and other debris away from the lungs

what does epithelium specialized to absorb substances do?

line some digestive system organs like the stomach

gland

cells that are adapted for secretion

secretions

contain proteins and is a specialty of the glands

Types of glands

pituitary, thyroid, adrenal, ovaries, testes, and pancreas

what does glandular epithelium do?

forms the glands in our body

what do secretions produce and secrete?

sweat, oil, digestive enzymes, mucus, and hormones

apical surface

the top surface of tissue that is exposed to the environment

basement membrane

the lower surface of the tissue

what does the basement membrane contain?

material secreted by the epithelial cells and the connective tissue cells that are next to the epithelium

epithelial tissue is ___?

avascular

what does avascular mean?

having no blood supply

since the epithelium is avascular, what does it rely on?

diffusion from the capillaries in the underlying connective tissue for food and oxygen

what is dense connective tissue referred to as?

fibrous tissue

what does dense connective tissue form?

strong, rope-like structures

what are the two major forms of dense (fibrous) tissue

tendons and ligaments

tendons connect what to what?

muscles to bones

ligaments connect what to what?

bones to bones

ligaments are __ than tendons?

stretchier

where can dense connective tissue also be found?

in the lower layers of the skin

what is the skin also called?

the dermis

how is the dense connective tissue in the lower layers of the skin arranged?

in sheets

characteristics of loose connective tissues?

is softer, has more cells, and fewer fibers

what are the two major types of loose connective tissue?

areolar and adipose

what is a tissue that is often called loose connective tissue?

reticular connective tissue

areolar tissue

the most widely distributed connective tissue in the body

what are the characteristics of areolar tissue?

is soft and pliable

what does areolar tissue form?

a cobweb that cushions and protects organs

functions of the areolar tissue?

serves as a packaging tissue and connective tissue “glue”. helps hold organs in their place and contains a watery solution

what happens when there is trauma to the watery solution in the areolar tissue?

the area swells and becomes puffy

what is the process of the area swelling and becoming puffy called?

edema

adipose tissue

tissue that is called fat

adipose tissue is areolar tissue that contains what?

fat cells

what does adipose tissue form?

subcutaneous tissue beneath the skin

what does the subcutaneous tissue do?

insulates the body and protects the skin from bumps and temperature changes

what does adipose tissue cushion?

the eyeballs in their sockets

where is adipose tissue found?

in the hips and breasts where fat is stored and available for fuel

what does reticular connective tissue consist of?

a network of interwoven reticular fibers

what does reticular connective tissue form?

stroma

what is the stroma?

the internal framework of organs

what does the stroma support?

blood cells in the lymphoid organs such as the lymph nodes, spleen, and bone marrow

what is reticular connective tissue also referred to as?

the blood or vascular tissue

why is reticular connective tissue considered as connective tissue?

it is surrounded by a nonliving fluid called plasma and composed of cells

what are the fibers of blood?

soluble proteins that become visible only during clotting

platelets

are responsible for clotting

blood is not a typical what?

connective tissue

what does blood work as?

the transport vehicle for the cardiovascular system

what does blood do?

carries nutrients, respiratory gases, and many other substances throughout the body

muscle tissue

contracts or shortens to create movement

types of muscle tissue

skeletal, cardiac, and smooth

skeletal muscle tissue

packaged by connective tissue sheets to form organs called skeletal muscles

skeletal muscles are attached to what?

the skeleton

skeletal muscles: voluntary or involuntary?

voluntary

what do skeletal muscles form?

the flesh of the body

what happens when the skeletal muscles contract?

they pull on the bones or skin and movement occurs

appearance of skeletal muscles

long, cylindrical, multinucleate, and have obvious striations

due to the long structure, skeletal muscles are called what?

fibers

where are cardiac muscles found?

in the heart

what happens as the heart contracts

it acts as a pump and propels the blood through the blood vessels

appearance of the cardiac muscles

have striations, cells are uninucleate, short, branching, and tightly fit together

intercalated disc

the junction where the cardiac muscles tightly fit together

what do the intercalated discs contain?

gap junctions that allow ions to pass freely from cell to cell

cardiac muscles: voluntary or involuntary

involuntary

appearance of smooth muscles

do not have striations that are visible, are spindle-shaped with a point at each end

what do smooth muscles have?

a single nucleus

where are smooth muscles found?

in the walls of hollow organs such as the stomach, uterus, and blood vessels

when smooth muscles contract and relax, what happens?

material is propelled through the organ

what is peristalsis?

a wave-like motion that keeps food moving through the small intestines

what are the four major shapes/classes of epithelium?

simple squamous, simple cuboidal, simple columnar, and pseudostratified

appearance of squamous cells

look like thin, flat plates that can look polygonal when viewed from above. closely fit together in tissues

what do squamous cells provide?

a smooth, low-friction surface over which fluids can move easily

where does the name “squamous” come from?

squama, Latin for “scale”

shape of the nuclei in squamous cells

usually correspond with the shape of the cell

what does the nuclei in squamous cells do?

help to identify the type of epithelium

squamous cells tend to have what kind of nuclei?

horizontally flattened, nearly oval-shaped nuclei

where are squamous cells found?

skin, alveoli, and lungs

shape of cuboidal epithelial cells?

cube-like

appearance of cuboidal epithelial cells?

square in cross-section

shape of nuclei in cuboidal cells

large, spherical, and in the center

shape of columnar epithelial cells

elongated and column-shaped

the height of columnar cells are what?

height is at least four times the width

what is the shape of the nuclei in columnar cells?

elongated

where are the nuclei of columnar cells usually located?

near the base of cells

what do columnar cells form?

the lining of the stomach and intestines

pseudostratified cells

simple columnar cells

how are the nuclei of pseudostratified cells?

they appear at different heights, giving the misleading impression that the epithelium is stratified when the cells are viewed in cross-section

what are ciliated pseudostratified epithelial cells?

epithelial cells that have cilia

nervous tissue

consists of nerve cells called neurons

what do neurons do?

receive and conduct impulses from one part of the body to another

what are the two functional characteristics of the nervous tissue?

irritability and conductivity

what is irritability?

the ability of a neuron to detect a stimulus and respond.

what is conductivity?

the ability of neurons to transmit signals to other neurons, muscles and glands.