Bio 125: Lecture 5

groups of closely associated cells that performs related functions and are similar in structure

• Epithelial tissue (epithelium)
• Connective tissue
• Nervous tissue
• Muscular tissue

sheets of cells covering body surface or lining a body cavity

• Includes C.T. proper (fats and ligaments), cartilage, bone, and blood
• provides support

• main components of the nervous system
• provides control

• includes skeletal, cardiac, and smooth muscle
• movement

organs such as the stomach, heart, kidneys, and lungs

the study of tissues.

the structural basis for a study of organ physiology

the tissue that covers the external body surface (epidermis), lines its cavities and tubules, and generally “marks off our insides from our outsides”

epithelial membranes

environments

• protections
• absorption
• filtration
• secretion
• sensory reception

• Cellularity
• Special Contacts
• Polarity
• Supported by connective tissue
• Avascular but innervated
• High regenerative capacity

composed almost entirely of cells

forms continuous sheets held together by tight junctions and desmosomes

apical (upper free) and basal (lower attached surfaces)

reticular and basal laminae (basement membrane)

epithelial tissue does not have blood vessels, but you may find receptor cells

rapidly replaces lost cells by cell division

• The arrangement or relative number of layers (first name of tissue)
• Cell shape (last name of tissue)

• simple
• stratified

consisting of one layer of cells attached to the basement membrane

consisting of two or more layers of cells

• squamous
• cuboidal
• columnar

cells wider than tall (plate-like)

cells are as wide as tall (cube-like)

cells are taller than they are wide (column-like)

• squamous: flat
• cuboidal: spherical
• columnar: oval

the cells at the apical surface of the epithelial membrane, not those resting on the basement membrane

Simple Columnar Epithelium

Stratified Cuboidal Epithelium

• Actually a simple columnar epithelium (one layer of cells), but… because its cells vary in height and the nuclei lie at different levels above the basement membrane… it gives a false appearance of being stratified.
• (This epithelium is often ciliated).

• Stratified squamous epithelium are formed of rounded, or “plump” cells with the ability to slide over another to allow the organ to be stretched
• Note: only found in urinary system organs… ex. Bladder
• Found in urinary system
• Bladder ———|
• Uterus ———| “Stretch”
• Urethra ———|
• Bladder is 6-cell layers when empty and 3-cell layers when full

single layer of flat cells with disc-shaped nuclei and sparse cytoplasm

Passage of material by passive diffusion and filtration and secretes lubricating substances in serosae (membranes)

slick lining of hollow organs

lines peritoneal, pleural, and pericardium cavities; covers visceral organs of those cavities

renal corpuscles, alveoli of lungs, lining of heart, blood and lymphatic vessels, lining of ventral body cavity (serosae)

single layer of cube-like cells with large, spherical central nuclei

secretion and absorption

kidney tubules, secretary portions of small glands, ovary surface

single layer of column-shaped (rectangular) cells with oval nuclei; some bear cilia at their apical surface; may contain goblet (mucus secreting) cells

Absorption; secretion of mucus, ion transport, ciliated type propels mucus or reproductive cells by ciliary action

• non-ciliated form lines digestive tracts, gallbladder, and ducts of small glands
• Ciliated form lines small bronchi, fallopian tubes, and uterus

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)

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

many layers of cells; superficial layers are squamous in shape while deeper layers of cells appear cuboidal or columnar; thickest epithelial tissue; adapted for protection

protects underlying tissues in areas subject to abrasion

• Keratinized forms- epidermis
• Non-keratinized forms- lining of esophagus, mouth, and vagina

generally two layers of cube-shaped cells

protection

forms largest ducts of sweat glands and forms ducts of mammary glands and salivary glands

several layers; basal cells usually cuboidal; superficial cells elongated

protection and secretion

rarest tissue type, found in male urethra and large ducts of some glands

basal cells usually cuboidal or columnar; superficial cells dome-shaped or squamous; undergoes transitions in shape

Stretches and permits distention of urinary bladder causing thinning (from 6 to 3 layers when filled with urine)

lines ureters, urinary bladder, and part of urethra

• many epithelial cells that make and secrete a product
• The product of a gland are aqueous fluids that usually contain proteins
• Epithelial cells forming glands are highly specialized to remove materials from the blood and to manufacture them into new materials, which they secrete (recall RER)

• The site of release: endocrine (“internally releasing”) vs. Exocrine (“externally releasing”)
• The relative number of cells forming the gland

• retain their ducts, and their secretions empty through these ducts to an epithelial surface. (internal and external)
• Local activity; diverse groups of glands

• lose their surface connection (duct) as they develop; thus they are referred to as “ductless glands”
• Secrete hormones directly into the blood or lymphatic vessels that weave through the glands to specific target organs far from the site of release

scattered within epithelial sheets

formed by invaginations or evaginations and usually have ducts tube-like connections to epithelial sheets) that carry products of exocrine glands to epithelial surface

• Scattered throughout epithelial lining of intestines and respiratory tubes, between columnar cells
• Goblet cells produce mucin, glycoprotein that dissolved H2O to become slimy (mucin + water = mucus); covers, protects, and lubricates many internal body surfaces

• Secretory unit
• Epithelium-walled duct

• Simple (unbranched)
• Compound (branched)

• Tubular (secretory cells form tubes)
• alveolar= acinar (secretory cells form small flask-like sacs)
• Tubuloalveolar (secretory cells form tubular and alveolar units)

• Adhesion proteins in the plasma membranes link together adjacent cells
• The wavy contours of the membranes of adjacent cells (tongue and groove)
• Special cell junctions

• A belt-like junctions that extends around periphery (apical region)
• Closes off extracellular space
• Some proteins in plasma membrane of adjacent cells are fused… preventing molecules from passing between cells of epithelial tissue

• An anchoring junction just below tight junctions
• Transmembrane linker proteins 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

• 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 plaques from cytoplasmic side

• 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)

• the border between the epithelia and the underlying C.T.
• Non-cellular supporting sheet of proteins secreted by epithelial cells

• Act as selective filter, determining which molecules from capillaries enter the epithelium
• Acts as scaffolding along which regenerating epithelial cells can migrate
• The basal lamina and reticular layers of the underlying connective tissue deep to it form the basement membrane

• 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.
• Thickening is especially evident in capillaries of kidneys and the retina of the eyes, making them nonfunctional. This is why kidney failure and blindness are major symptoms of diabetes

• finger-like extensions of plasma membrane
• Maximizes surface area across which small molecules enter or leave
• Abundant in epithelia of small intestine and kidney

• whip-like, highly motile extensions of apical surface membranes
• Axoneme- a set of microtubules; contains a core of nine pairs of microtubules encircling one middle pair; each pair of microtubules arranged in a doublet
• Movement of cilia: in coordinated waves

• extremely long cilia used to propel cells/ organisms
• Example: sperm cells
• Movement of flagella: whiplike pattern