Semester Exam: histology epithelial tissue Flashcards
tissues
Cells work together in functionally related groups called tissues
types of tissues
Epithelial – lining and covering
Connective – support
Muscle – movement
Nervous – control
general characteristics of epithelial tissues
Covers a body surface or lines a body cavity
Forms most glands
Functions of epithelium
Protection (resist friction)
Absorption, secretion, and ion transport
Filtration (kidneys)
Forms slippery surfaces (to resist friction, lungs and heart)
Special Characteristics of Epithelia
Cellularity Specialized contacts Polarity Support by connective tissue Avascular Innervated Regeneration
Cellularity
cells are in close contact with each other with little or no intercellular space between them
Specialized contacts
may have junctions for both attachment and communication
Polarity
epithelial tissues always have an apical (toward top/lumen) and basal surface (towards bottom and near connective tissue)
Support by connective tissue
held in place or supplied with blood and nutrients
Avascular
no blood supply so nutrients must diffuse
Innervated
has nerve endings
Regeneration
epithelial tissues have a high capacity for regeneration, think of skin
what makes up the basement membrane
the basal lamina and the connective tissue contribute to the basement membrane
Lateral Surface Features/ Factors holding epithelial cells together
Adhesion proteins link plasma membranes of adjacent cells Contours of adjacent cell membranes Special cell junctions (Tight Junctions Adherens Junctions Desmosomes)
basal lamina
Noncellular supporting sheet between the epithelium and the connective tissue deep to it
Consists of proteins secreted by the epithelial cells
basal lamina function
Acts as a selective filter, determining which molecules from capillaries enter the epithelium
Acts as scaffolding along which regenerating epithelial cells can migrate
First name of tissue indicates
number of layers
simple-one layer
stratified- more than one layer
Last name of tissue describes
shape of of cells
Squamous
cells wider than tall (plate or “scale” like)
Cuboidal
cells are as wide
as tall, as in cubes
Columnar
cells are taller than
they are wide, like columns
naming of epithelial
Naming the epithelia includes both the layers (first) and the shape of the cells (second)
may also include accesssory structures
accesssory structures
Goblet cells
Cilia
Keratin
Special epithelial tissues (don’t follow naming convention)
Psuedostratified- look stacked but not
Transitional- look cuboidal or squamish
Simple Squamous Epithelium description
single layer of flat cells with disc-shaped nuclei
Simple Squamous Epithelium special types
Endothelium (inner covering)
Mesothelium (middle covering)
Simple Squamous Epithelium function
Passage of materials by passive diffusion and filtration
Secretes lubricating substances in serosae
Simple Squamous Epithelium location
Renal corpuscles (kidneys)
Alveoli of lungs (cluster of air sacs)
Lining of heart, blood and lymphatic vessels
Lining of ventral body cavity (serosae)
Endothelium
(inner covering)
slick lining of hollow organs
Mesothelium
(middle covering)
Lines peritoneal( abdominal), pleural (lungs), and pericardial (heart) cavities
Covers visceral organs of those cavities
Simple Cuboidal Epithelium description
single layer of cube-like cells with large, spherical central nuclei
Simple Cuboidal Epithelium function
secretion and absorption
Simple Cuboidal Epithelium location
kidney tubules, secretory
portions of small glands,
ovary & thyroid follicles
Simple Columnar Epithelium description
single layer of column-shaped (rectangular) cells with oval nuclei
Some bear cilia at their apical surface
May contain goblet cells (contains mucin)
Simple Columnar Epithelium function
Absorption; secretion of mucus, enzymes, and other substances
Ciliated type propels mucus or reproductive cells by ciliary action
Simple Columnar non ciliated Epithelium location
Lines digestive tract,
gallbladder, ducts of
some glands
Simple Columnar ciliated Epithelium location
Lines small bronchi,
uterine tubes (aka:
Fallopian tubes/ oviducts), uterus
Pseudostratified Columnar Epithelium description
All cells originate at basement membrane Only tall cells reach the apical surface May contain goblet cells and bear cilia Nuclei lie at varying heights within cells Gives false impression of stratification
Pseudostratified Columnar Epithelium function
secretion of mucus; propulsion of mucus by cilia
Pseudostratified Columnar non ciliated Epithelium location
Ducts of male reproductive tubes
Ducts of large glands
Pseudostratified Columnar ciliated Epithelium location
Lines trachea and most of upper respiratory tract
Stratified Epithelia
Contain two or more layers of cells
Regenerate from below
Stratified Epithelia main role and how named
Major role is protection
Are named according to the shape of cells at apical layer
Stratified Squamous Epithelium description
Many layers of cells – squamous in shape
Deeper layers of cells appear cuboidal or columnar
Thickest epithelial tissue – adapted for protection
Stratified Squamous Epithelium specific types
Keratinized – contain the protective protein keratin
Surface cells are dead and full of keratin
Non-keratinized – forms moist lining of body openings
Stratified Squamous Epithelium function
Protects underlying tissues in
areas subject to abrasion
Stratified Squamous Epithelium location
Keratinized – forms epidermis
Non-keratinized – forms lining of
esophagus, mouth, and vagina
Transitional Epithelium description
Basal cells usually cuboidal or columnar
Superficial cells dome-shaped or squamous
Transitional Epithelium function
stretches and permits distension of urinary bladder
Transitional Epithelium location
Lines ureters, urinary bladder and part of urethra
Glandular Epithelium
Ducts carry products of exocrine glands to epithelial surface
maybe multicelular or unicellular
Glandular Epithelium include following diverse glands
Mucus-secreting glands (uni) Sweat and oil glands Salivary glands Liver and pancreas Mammary glands
exocrine
ducted, secret into ducts
endocrine
ductless, secret right into blood stream
Unicellular Exocrine Glands
The Goblet Cell
Goblet cells produce mucin
Mucin + water = mucus
Protects and lubricates many internal body surfaces
mucin
condensed as
“granules” which rapidly expand like shaving cream when excreted
Multicellular Exocrine Glands
Classified by structure (branching & shape) of duct
Can also be classified by mode or type of secretion
May also be classified by types of secretions from exocrine glands
Merocrine secretion
secretory vesicles released via exocytosis (saliviary glands)
Apocrine secretion
apical portion of the cell is lost, cytoplasm + secretory product (mammary glands)
Holocrine secretion
entire cell is destroyed during secretion (sebaceous gland)
Serous
mostly water but also contains some enzymes
Ex. parotid glands, pancreas
digestion or lubrication
mucous
mucus secretions
Ex. sublingual glands, goblet cells
sinuses and trachea
mixes of mucous and serous
serous & mucus combined
Ex. submandibular gland
simple gland
one attached to duct
branched gland
more than one, attached to one duct
compound gland
more than one unit attached to duct
simple alviola gland shape
tube with circle
simple tubular gland shape
tube
The three major types of epithelial membranes are
serous, mucous, and cutaneous. A fourth is the synovial membrane that lines the joints.
serous membrane
aids in digestion, lines lungs and heart
mucous membrane
sinus, trachea, nasal
cutaneous membrane
skin
