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Groups of closely associated cells that perform related functions and are similar in structure
The study of tissues
The tissues that covers the external body surface (epidermis), lines its cavities and tubules, and generally ""marks off our insides from our outsides
Functions of Epithelia?
Protection, absorption, filtration, secretion, and sensory reception.
Unique characteristics of Epitheial tissues, and what they are?
- 1) Celluratiy- composed almost entirely of cells
- 2) Special contacts - form continuous sheets held together by tight junctions
- and desosomes
- 3) Polarity - apical (upper free) and basal (lower attached) surfaces
- 4) Supported by connective tissue - Reticular and basal laminae (basement
- 5) Avascular but innervated- no blood vessels but there are receptors
- 6) High regenerative capacity - rapidly replaces lost cells by cell division
Epithelia are classified into what categories?
- 1) Arrangement or relative number of layers
- 2) cell shape
What are the cell shapes, and descriptions?
- 1) Squamous : cells wider than tall (plate-like)
- 2) cuboidal: cells are as wide as tall (cube-like)
- 3) columnar : cells are taller than they are wide (column-like)
What are 2 other types of epithelia that are less easily categorized?
- 1) Pseudostratified epithelium- Actually a simple columnar epithelium,but... because its cells vary in height and the nucleei lie at different levels above the basement membrane.... it gives a false appearance of being stratified.
- 2) Transitional epithelium - Stratified squamous epithelium are formed or rounded, or ""plump"" cells with the ability to slide over one another to allow the organ to be stretched. ONLY FOUND IN URINARY SYSTEM ORGANS like the bladder
What is the function and types of Simple squamous epithelium?
- Function - Passage of materials by Passive diffusion and filration and secretes lubricating substances in serosae (membranes)
- Special Types:
- 1) Endothelium (inner covering) -Slick linging of hollow organs
- 2) Mesthelium (middle covering) - lines peritoneal, pleural, and pericardial
- cavities; covers visceral organs of those cavities
What is some main locations of Simple squamous epithelium?
Renal corpuscles, alveloi of lungs, lining of heart, blood and lymphatic vessels, lining of ventrala body cavity.
What is the function of Simple cuboidal epithelia, and locations?
Secretion and absorption
Kidney tubules, secretory portions of small glands, ovary surface
What is the function, and locations of simple columnar epithelium?
Absorption; secretion of mucus, ion transport, ciliarted type propels mucus or reproductive cells by ciliary action.
- Non-ciliated form - lines digestive tract, gallbladder, ducts
- of some glands.
Ciliated form lines small bronchi, fallopian tubes, and uterus
What is the function of Pseudostratified columnar epithelia, as well as some locations?
Secretion of mucus; propulsion of mucus by cilia
Non-ciliated form is in ducts of male reproductive tubes and ducts of large glands
Ciliated form lines trachea and most of upper respiratory tract
What are the functions of Stratifited squamous Epithelium and some locations?
Protects underlying tissues in areas subject to abrasion
- Keratinzied forms - epidermis
- Non-keratinized forms - lining of esophagus, mouth and vagina
What is the function of Stratified Cuboidal Epithelium and what are some locations?
Forms largest ducts of sweat glands and forms ducts of mammary glands and salivary glands.
what is the function of stratified columnar epithelium, and what are some locations?
- Protection and secretion
- Rarest tissue type, found in male urethra and large ducts of some glands
What is the fuction of transitional epithelium, and what are some locations?
Stretches and permits distension of urinary bladder casuing thinning (from 6 to 3 layers when filled with urine)
Lines ureters, urinary bladder and part of urethra.
What is a gland, and what do they make?
- it is many epithelial cells that make and secrete a product.
- -The products of a gland are aqueous fluids that usually contain proteins
What are epithelial cells that form glands, specialized for?
To remove marterial from the blood and to manufacture them into new materials, which they secrete (recall RER)
What classifies glands?
- -the site of release: Endocrine (internally releasing) vs Exocrine (externally releasing)
- - the relative number of cells forming the gland
In terms of ducts, what is unique about Endocrine glands, and what do they do with the hormones?
They lose their surface connection (duct) as they develop; thus they are referred to as "ductless glands".
They secrete hormones directly into the blood or the lymphatic vessels that weave through the gland to specific TARGET ORGANS far from the site of release.
As same question but with EXOCRINE GLANDS.
They retain their ducts, and their secretions empty through these ducts to an epithelial surface. (Internal and external)
Aside from the sites of product release, what are the classifications based the relative number of cells forming the gland?
- 1) Unicellular: scattered within epithelial sheets
- 2) Mulitcellular: formed by invaginations or evaginations and usually have DUCTS that carry products of exocrine glands to epithelial surface.
What is the nickname for Unicellular Exocrine glands, and why?
- Goblet cells
- because they are in the shape of a goblet.
Where are unicellular exocrine glands usually located?
Throughout the lining of intestines and respiartory tubes between columnar cells
What do goblet cells, and what do they do?
They produce mucin, which covers, protects and lubricates many internal body surfaces.
What parts do multicellular exorcrine glands have?
They have two basic parts: Secretory unit, and Epithelium-walled duct
Based on the parts, what classifications do the parts have?
- Based on the structure of the duct, there is Simple (unbranched), and Compound (branced)
- Then based on the secretory unit structure:
- 1) Tubular (secretory cells form tubes)
- 2) Alveolar = Acinar (secretory cells form small flask-like sacs)
- 3) Tubuloalveolar (secretory cells form tubular and alveolar units)
What three factors act to bind epithelial cells to one another?
- 1) Adhesion proteins in the plasma membranes link together adjacent cells
- 2) The wavy contours of the membranes of adjacent cells (tongue and groove)
- 3) Special cell junctions (tight junctions, adherens junctions, desmosomes, gap junctions)
What are some features of Tight Junctions (zonula occludens)?
- -A belt-like junction that extends around periphery (apical region)
- -Closes off extracellular space
- -some proteins in plasma membrane of adjacent cells are fused, thus preventing molecules from passing between cells of epi. tissue
What are some features of Adherens junctions (Zonula adherens)?
- -An anchoring junction just below tight junctions
- -Transmembrane linker protein attach to actin microfilaments of the cytoskeleton and bind adjacent cells
- -With tight junctions, form the tight junctional complex around apical lateral borders of epithelial tissues
What are the features of Desmosomes (anchoring junctions)?
- -THey are the main junctions for binding cells together
- -two disc-like plaques connected across intercellular space
- -Plaques of adjoining cells are joined by proteins called cadherins
- -proteins interdigitate into extracellular space
- -intermediate filaments insert into plaques from cytoplasmic side
What are some features of Gap junctions (nexus)?
- -Tunnel-like passageway between two adjacent cells (anywhere)
- -Let small molecules move directly between neighboring cells
- -cells are connected by hollow cylinders of protein (connexons)
What is the basal lamina and what are some functions?
It is the border between the epithelia and the underlying C.T. (non-cellular supporting sheet of proteins secreted by epithelial cells
- -Acts as a selective filter, determining which molecules from capillaries enter the epithelium
- -Acts as scaffolding along which regenerating epithelial cells can migrate
What do the basal lamina and reticular layers form?
the basement membrane
What happens in untreated cases of Diabetes mellitus?
The basement membranes associated with endothelium of capillaries thicken over time, probably because that take up glucose which is present in very high concentrations
What is the symptoms of Diabetes Melltus, and why?
Kidney failure and blindness are symptoms of dabetes. Reason is that thickening is especially evident in capillaries of kidneys and the retina of eyes, making them nonfunctional.
What are some appendage of the apical surface?
Microvilli, cilia, flagella
What are some features of microvilli?
- -Finger-like extensions of plasma membrane
- -Maximizes surface area across which small molecules enter or leave
- -Abundant in epithelia of small intestine and kidney
What is a characteristic feature of Cilia? what are some parts?
- -Whip-like, highly motile extensions of apical surface membranes
- -Axoneme a set of microtubles; contains a core of nine pairs of microtubules encircling one middle pair; each pair of microtubules arranged in a doublet
What is the movement of cilia?
Coordinated waves of power strokes and recovery strokes
What is flagella, and what is the movement?
- -Extremely long cilia used to propel cells/ organisms (eg. sperm cells)
- -Whiplike pattern
What is connective tissue? What are some functions? What are some examples?
- -It found in all parts of the body as discrete structures or as part of various body organs
- -its functions is to Protect, support (cartilage and bone), and bind together (tendons and ligaments) other tissues of the body.
- 1) Osseous tissue: connective tiusse of bones
- 2) Areolar connective tissue: soft packaging material that cushions and protects body organs
- 3) Adipose (fat) tissue: provides insulation of the body tissues and a source of stored food
- 4) Hematopoietic tissue: replenished the bodys supply of red blood cells
What are the four main types of connective tissue?
- 1) connective tissue proper- fat tissue and fibrous tissue of ligaments
- 2) cartilage
- 3) bone tissue
- 4) blood
Where do all types of connective tissue originate from?
What do connective tissues GENERALLY have?
what are some exceptions?
- -A rich supply of blood vessels
- -Exceptions include: cartilage, tendons, and ligaments
What is between the cells of connective tissue?
A vast amount of noncellular (non-living material), called the extracellular matrix
How does the ECM distinguish connective tissue from all other tissues?
- The is produced by the cells and then extruded.
- The matrix accounts for the strength of connective tissue