What are the three general functions of epithelium?
Absorption, secretion, and providing a barrier
What are the four basic types of tissue?
Epithelial, muscle, nervous, and connective
Which general function of epithelium is a function of ALL epithelium?
Providing a barrier
What produces the basal lamina of the basement membrane?
Epithelium
What are the three specialized functions of epithelium?
Transfer molecules across epithelium, prevent transfer of materials (aka selective permeability), sensory function
What produces the reticular lamina in the basement membrane?
Fibroblasts in connective tissue
What are the two parts of the basement membrane of epithelium?
Basal lamina and reticular lamina
What makes up a partial basement membrane of epithelium?
Basal lamina ONLY
What are the functions of the basement membrane of epithelium?
Providing a surface for epithelial cell attachment, molecular filter (very limited), limits stretch, and directs migration of cells
Are epithelial cells vascular or avascular?
Avascular
By what process do epithelial cells obtain nutrition?
Diffusion
What are the functions of connective tissue?
Provides nutrition (and oxygen), source of defensive cells
Which type of cell junction involves the sharing of intrinsic membrane proteins between adjacent cells?
Zonula occludens
What is the other name for zonula occludens?
Tight junction
What are the functions of zonula occludens (tight junctions)?
Provides strong attachment, prevents the passage of materials between cells
Zonula adherens consist of what?
Cadherins (linkage proteins) and marginal bands (microfilaments)
What part of the zonula adherens are located between cells?
Cadherins
What is the other name for zonula adherens?
Adhesion belt
What part of the zonula adherens attach the cytoskeleton to the cell membrane?
Marginal bands
What are the functions of the zonula adherens?
Strong attachment and provide cell structural stability
What is another name for macula adherens?
Desmosome
What is the function of macula adherens?
Provides strong attachment
What are the three parts of the macula adherens?
Transmembrane proteins, protein plaque, and tonofilaments
Which type of cell junction is arranged in a cylinder with six connexins (proteins)?
Gap junctions
What are the two functions of gap junctions?
Strong attachment, transport materials between cells
What makes up the junctional complex (in order)?
Zonula occludens, zonula adherens, macula adherens
What junctions hold the epithelium to the basement membrane and the connective tissue below?
Hemidesmosomes and focal point contacts
What is the function of hemidesmosomes?
Helps connect epithelial cells to the basal lamina (essentially half a desmosome)
What is bullous pemphigoid?
An autoimmune skin disease causing large blistering lesions that burst but do heal
What is pemphigus vulgaris?
An autoimmune skin disease causing skin blistering that do not heal easily; excessive bleeding is likely & can be fatal
What is cholera?
Acute bacterial infection of the small intestines
What is the cause of bullous pemphigoid?
Antibodies bind to some proteins in hemidesmosomes
What is the cause of pemphigus vulgaris?
Antibodies bind to some parts of desmosomes
What is the cause of cholera?
Toxins disrupt proteins in the zonula occludens which permits the loss of water and electrolytes from the connective tissue below the epithelium
What is the general name for the type of epithelium that is one cell thick?
Simple epithelium
What type of simple epithelium is a single layer of flattened cells?
Simple squamous
What type of epithelium is found in the lungs, parietal layer of the Bowman’s capsule in the kidney, and the serosa on the outside of organs?
Simple squamous
What are the functions of simple squamous epithelium?
Living filter, provide a barrier
What type of simple epithelium is located in exocrine ducts, thyroid follicular cells, and the proximal and distal convoluted kidney tubules?
Simple cuboidal
What are the functions of simple cuboidal epithelium?
Absorption, secretion, provide a barrier
What type of simple epithelium is one layer of cube shaped cells?
Simple cuboidal
What type of simple epithelium represents a single layer of rectangular shaped cells that appear vertical?
Simple columnar
What type of epithelium is located in the stomach, small intestines, gallbladder, colon, and larger exocrine ducts?
Simple columnar
What are the functions of simple columnar epithelium?
Absorption, secretion, provide a barrier
What type of simple epithelium is also known as respiratory epithelium?
Ciliated pseudostratified columnar epithelium
What type of simple epithelium is located in the trachea, respiratory region of nasal cavity, and the bronchi?
Ciliated pseudostratified columnar epithelium
What is the function of goblet cells?
Produce and secrete mucus
Ciliated pseudostratified columnar epithelium is made up of what three types of cells?
Goblet cells, ciliated columnar cells, and basal cells
What is the function of the ciliated columnar cells found in ciliated pseudostratified columnar epithelium?
To move mucus over the membrane
What type of cell in respiratory epithelium does not reach the surface?
Basal cells
What is the function of the basal cells of respiratory epithelium?
To be the stem cell of that type of epithelium (proliferation and differentiation)
What are the finger like projections at the apical surface on some epithelial cells?
Microvilli (brush border or striated border)
What is the function of microvilli?
To increase surface area so as to increase absorption
What are good example locations of microvilli?
Kidney tubule cells and small intestines
What are extremely long microvilli?
Stereocilia
Where can stereocilia be found?
Epididymis, cochlear hair cells
What is the function of stereocilia?
To increase surface area
Are stereocilia considerably motile?
No, less motile; they are actually quite rigid with actin core (not related to true cilia)
What is the function of cilia?
To move something over a surface
What are the apical hair-like extensions of the cytoplasm that function in movement?
Cilia
What are good examples of ciliary locations?
Trachea and fallopian tube
What organelle is largely seen in cilia?
Mitochondria
What anchors cilia?
Basal bodies
What is the result of basal bodies in cilia blocking the free surface?
No absorption or secretion
What is the surface layer of glycoproteins and carbohydrates that covers some epithelium?
Glycocalyx
What produces the glycocalyx?
Epithelial cells
What are the functions of the glycocalyx?
Protection and cell recognition
What are other possible functions of the glycocalyx?
Cell adhesion and holds enzymes
What are example locations of the glycocalyx?
Stomach and small intestines
What type of epithelium is two or more cell layers thick?
Stratified epithelium
What is the general function of all stratified epithelium?
Protection
Types of stratified epithelium are named after what cells?
Superficial layer of cells
What type of stratified epithelium has multiple layers of cells that seem to flatten out from the basal layer to the superficial layer & the superficial layer of cells are flat and alive?
Stratified squamous epithelium
What type of epithelium is found in the esophagus, oral cavity, tongue, and vagina?
Stratified squamous epithelium
What is the general function of stratified squamous epithelium?
Protection from abrasion/friction
What is the type of epithelium of the skin?
Keratinized stratified squamous epithelium
What are some limitations of stratified squamous epithelium?
No protection from drying and limited thickness leading to limited protection
What is the function of keratinized stratified squamous epithelium?
Protection in a dry environment
What are the layers of the skin?
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
Which layer of the skin is made of dead cells, keratin, and lipids?
Stratum corneum
What are the three general functions of the stratum corneum?
Prevents water loss, provides a barrier to microbes, protects against abrasion
Which two layers of the skin are layers where cell division can occur?
Stratum basale and stratum spinosum
Which layer of the skin is closest to the dermis and is made up of 1-2 layers of mitotic keratinocytes?
Stratum basale
Where are melanocytes found?
Stratum basale
What is the general function of melanocytes?
Protect from UV radiation
What cells determines skin color?
Melanocytes
Which type of melanin is known to represent darker pigments?
Eumelanin
Which type of melanin represents a reddish color?
Pheomelanin
What three things influence skin color?
Environment, genetics, number of blood vessels in the dermis
True or false: everyone has the same number of melanocytes.
True! The difference is the production of melanin of each melanocyte
Where are Langerhans cells located?
Stratum spinosum
What is the function of the Langerhans cells?
Recognize and process foreign antigens (APC)
What effect does UV radiation have on Langerhans cells?
Reduction
What type of epithelium can be found in the sweat and salivary glands?
Stratified cuboidal epithelium
What effect does repeated UV exposure have on melanocytes?
Increased numbers
What are the functions of stratified cuboidal epithelium?
To increase protection and provide a barrier
What are the functions of stratified columnar epithelium?
Increase protection, provide a transition between epithelial types, provide a barrier
What cells are known as the epithelial tactile cells?
Merkel cells
Merkel cells are located in what layer of the skin?
Stratum basale
What layer of the skin is associated with free nerve endings?
Stratum basale (due to Merkel cells)
The function of taste buds and the retina of the eye are examples of what specialized function that can be possessed by epithelium?
Sensory
What transmembrane protein of the cell membrane binds to structural connective tissue glycoproteins and also connects to cytoskeleton?
Integrin (focal point contacts)
During the stem cell division of one basal cell of respiratory epithelium, what are the two daughter cell types?
One basal cell and one goblet cell/ciliated columnar cell (2 total)
What covers the superficial cell layer of keratinized stratified squamous epithelium?
Nonliving layer of keratin
What is another term for the stratum basale?
Stratum germinativum
Which layer of the skin contains multiple layers of “spiny shaped” keratinocytes?
Stratum spinosum
What do the keratinocytes found in the stratum spinosum produce?
Lipids and keratohyaline vacuoles
In which layer of the skin does exocytosis of lipid-filled lamellar granules occur?
Stratum granulosum
Which layer of the skin is only present in thick skin, is difficult to see, and does not contain nuclei or organelles?
Stratum lucidum
What structures contribute strength to keratinized stratified squamous epithelium by increasing surface area of attachment of the epithelium to the connective tissue below?
Epidermal pegs (rete ridges)
What is the relative half life of skin cells?
28 days
What type of epithelium is likely to be seen in the large ducts in the pancreas, parts of the male urethra, and the conjunctiva of the eye?
Stratified columnar
What is the appearance of the basal layer of stratified columnar epithelium?
Flattened to cuboidal in shape
What is the frequency of stratified columnar epithelium in the body?
Rare
What is another name for transitional epithelium?
Urinary epithelium or urothelium
What is the microscopic appearance of the basement membrane and nuclei of transitional (urinary) epithelium?
Straight basement membrane and round nuclei
What type of epithelium makes up most of the urinary tract?
Transitional epithelium
What are the functions of transitional (urinary) epithelium?
Provide protection, to stretch, act as a barrier
What is the basement membrane structure of transitional epithelium?
Thin and fenestrated
What type of cell junction is well-developed with transitional (urinary) epithelium?
Zonula occludens (tight junctions)
Why is it important for transitional (urinary) epithelium to have well-developed tight junctions?
Extra support is needed due to the fenestrated basement membrane, prevents wastes/urine from seeping between epithelial cells
What is the unusual superficial cell feature of transitional (urinary) epithelium?
Presence of some bi-nucleated superficial cells
Why do the cells of transitional (urinary) epithelium obtain more oxygen?
Due to fenestrated basement membrane and decreased diffusion distance when stretched