physical barrier, selective permeability, establish electrochemical gradients, and contains receptors for communication

1. Peripheral protein
2. Integral protein
1. Transmembrane protein
1. Glycoprotein
2. Ion-specific channel protein
3. Carrier/transporter protein

1. Endocytosis
2. 3 major types of endocytosis

1. Bulk movement of substance into the cell by vesicles forming at the plasma membrane.
2. phagocytosis, pinocytosis, receptor-mediated endocytosis

Type of endocytosis in which vesicles are formed as particulate materials external to the cell are engulfed by pseudopodia.

Ex. Certain white blood cells, such as macrophages and neutrophils, are specialized for engulfing and removing particulate matters such as bacteria, protozoa, dead cells, and unneeded extracellular constituents.

Pseudopodia are extended in an actin-dependent process.

The resulting intracellular vacuole is called a phagosome, which fuses with lysosome for degradation.

Type of endocytosis in which vesicles are formed as interstital fluid is taken up by the cell.

Ex. Formation of small vesicles in capillary wall to move substances.

Non-specific, intake of ECF and dissolved particles only.

Transcytosis: process of bulk transfer of material across the cell

Type of endocytosis in which plasma membrane receptors first bind specific substances; receptor and bound substance then taken up by the cell.

Ex. Uptake of cholesterol, Fe, and vitamin B12 into cells

Many diseases are caused by defective receptors.

Ex. pseudohypoparathyroidism (nonfunctioning parathyroid receptors), one type of dwarfism (nonfunctioning growth hormone receptors), and type 2 diabetes (nonfunctioning insulin receptors)

The glands produce the respective hormones, but the target cells can't respond because they lack normal receptors.

Organelles composed of both protein and ribosomal RNA (rRNA) that are organized into both a large and small subunit; may be bound (ex. rough ER) or free in cytosol.

• Free ribosomes
• Synthesize cytosolic and cytoskeletal proteins
• Synthesize proteins for import into the nucleus, mitochondria, and peroxisomes.
• Bound ribosomes
• Synthesize proteins that are to be incorporated into membranes, stored in lysosomes, or eventually secreted from the cell.

Misfolded proteins are conjugated to ubiquitin and targeted for proteasomal degradation.

Extensive interconnected membrane network that varies in shape (ex. cisternae, tubules) and ribosomes are attached on cytoplasmic surface.

Modifies, transports, and stores proteins produced by attached ribosomes; these proteins are secreted, become components of the plasma membrane, or serve as enzymes of lysosomes.

Extensive interconnected membrane network lacking ribosomes.

Synthesizes, transports, and stores lipids (ex. steroid, phospholipid)

Metabolizes carbohydrates

Detoxifies drugs, alcohol, and poisons

Forms vesicles and peroxisomes

Temporary sequestrate Ca²⁺

Quality control during protein production in the RER and properly functioning ER associated degradation (ERAD) to dispose of defective proteins are extremely important and several inherited diseases result from malfunctions in this system.

In some forms of osteogenesis imperfecta bone cells synthesize and secrete defective procollagen molecules which can't assemble properly and produce very weak bone tissue.

Very little RER with essentially all polyribosomes free in the cytoplasm.

Ex. erythroblast

Have RER, a Golgi apparatus, and a supply og secretory granules or vesicles containing the proteins ready to be secreted.

Ex. eosinophilic leukocyte

Morphology of cells where proteins undergo immediate exocytosis

Have extensive RER and a well-developed Golgi apparatus with few secretory granules.

Ex. plasma cell

Have distinct polarity, with RER abundant at their basal ends and mature secretory granules at the apical poles undergoing exocytosis into the lumen of a gland.

Ex. pancreatic acinar cell

Jaundice

Yellowish discoloration of the skin

Caused by accumulation in ECF of bilirubin and other pigmented compounds, which are normally metabolized in liver (SER enzymes) and excreted as bile.

A frequent cause in newborn infants is an underdeveloped state of SER in liver cells, with failure of bilirubin to be converted to a form that can be readily excreted.

Organelle consisting of stacked membraneous cisternae in which proteins made in RER are processed further and packaged for secretion or other roles.

Originating as condensing vesicles in the Golgi apparatus, secretory granules are found in cells that store a product until its release by exocytosis is signaled by a metabolic, hormonal, or neural message (regulated secretion).

A technique used to cytologically map the locations of genes or other DNA sequence within large eukaryotic chromosomes. In this method, a complementary probe is used to detect the location of a gene within a set of chromosomes

Microtubules

1. Structure
2. General location
3. Major function

1. Hollow tube with a wall of 13 parallel protofilaments; composed of alpha and beta tubulin
2. Radiating through cytoplasm from concentration at centrosomes; axonemes (cilia and flagella)
3. Maintain cell shape, rigidity, and polarity; organize and move organelles (tracks for motor proteins: kinesins and dyneins); support cilia and flagella; participate in vascular transport; separate chromosomes during the process of cell division

Microfilaments

1. Structure
2. General locations
3. Major functions

1. Composed of globular G-actin monomers that assemble in the presence of K⁺ and Mg⁺ into a double stranded helix of filamentous F-actin. The G-actin subunits are added to the (+) end and removed at the (-) end. (treadmilling)
2. Concentrated beneath cell membrane; in cell extensions like microvilli.
3. Maintain cell shape; support microvilli; separate two cells during cytokinesis (a process of cell division); facilitate change in cell shape (ex. pseudopod extension); participate in muscle contraction

Intermediate filament

1. Structure
2. General locations
3. Major functions

1. Cable of 4 intertwined protofibrils, each consisting of bundled tetramers associated end to end. It is composed of various protein subunits in different cells such as vimentin, nuclear lamins, neurofilament proteins, and keratins
2. Arrayed throughout cytoplasm; at desmosomes (macula adherens); inside nuclear envelope
3. Strengthen cell and tissue structure; maintain cell shape; maintain nuclear shape (lamins)

Peroxisomes

1. Structure
2. Major Function

1. Small, spherical shaped membrane bound organelles formed form the ER or through fission; contain oxidative enzymes
2. Detoxify specific harmful substances either produced by the cell or taken into the cell; engage in beta oxidation of fatty acids to acetyl CoA

secretory granules with dense contents of digestive enzymes

Lysosomal storage disorders

1. Cause and result
2. 5 examples of disorders and the tissues affected

1. Stem from defects in one or more of the digestive enzymes present in lysosomes (synthesized in RER), usually due to a mutation leading to a deficiency of one of the enzymes, or defects due to faulty posttranslational processing. This results in large accumulation of secondary lysosomes or large residual bodies, interferring with normal cell/tissue function.
2. disease:tissue affected
   

Hurler syndrome (MPS 1): skeleton & nervous sys.

McArdle syndrome: skeletal muscle

Tay-Sachs: nervous system

Gaucher: liver and spleen

I-cell disease: skeleton and nervous system

Secondary lysosome can be formed by fusing primary lysosome with _1_, _2_, and _3_.

1. late endosome
2. phagocytic vacuole
3. autophagosome

Failure of proteasomes or toher aspects of a cell's protein quality control can allow large aggregates of protein to accumulate in affected cells. Such affrefates may adsorb other macromolecules to them and damage or kill cells. The aggregates that are released can then accumulate in ECM.

In the brain this can interfere directly with cell function and lead to neurodegeneration. Alzheimer disease and Huntington disease are two neurologic disorders caused initially by such protein aggregates.

In order to block activity of mitotic spindle in rapidly growing neoplastic cells for cancer therapy, which components of the cell should be inhibited?

Centrosome, specifically dynamics of microtubules.

How can we identify the tissue of origin for a cancerous tumor that has metastasized?

By looking for the presence of a specific type of intermediate filament. Identification of intermediate filament proteins by means of immunocytochemical methods is a routine procedure.

Ex. use of GFAP to identify astrocytomas (common type of brain tumor)

The process by which redundant or defective cells are rapidly eliminated in a manner that doesn't provoke a local inflammatory reaction in the tissue.

All substances that enter or leave tissues and organs must cross ___.

an epithelium

This is because epithelial cells line all external and internal surfaces of the body.

• tightly packed
• avascular
• form sheets, line, cover, protect
• secrete and absorb
• myoepithelia can contract

A thin EC layer of specialized proteins, usually having 2 parts: a basal lamina and a more fibrous reticular lamina

A thin meshwork of type IV collagen and laminin produced by the epithelial cells.

laminin: lacey glycoprotein in layer anchored by transmembrane integrins

Ex. hemidesmosomes with receptors for laminin and type IV collagen

type IV collagen: smooth layer beneath laminin

The laminin and type IV collagen networks are held together by the adhesive glycoprotein _1_ and proteoglycan _2_.

1. entactin
2. perlecan

Contains type III collagen and anchoring fibrils of VII collagen, all secreted by cells of the immediately adjacent connective tissue.

• attach epithelia to connective tissue
• regulate substance passing from connective tissue into epithelia
• provide a guide or scaffold during tissue regeneration after injury
• compartmentalize epithelial cells from other tissues

Tight Junction (Zonula Occludens)

1. Cytoskeletal compartments
2. Major functions
3. medical significance

Occluding junction

1. actin filaments
2. seals adjacent cells to one another, controlling passage of molecules between them; separates apical and basolateral membrane domains
3. defects in occludins (one of the major transmembrane link proteins) may compromise the fetal blood-brain barrier, leading to severe neurologic disorders

Adherent Junction (Zonula Adherens)

1. Cytoskeletal compartments
2. Major functions
3. medical significance

Anchoring junction

1. actin filaments
2. provides points linking the cytoskeletons of adjacent cells; strengthens and stabilizes nearby tight junctions
3. loss of E-cadherin (one of the transmembrane link proteins) in epithelial cell tumors (carcinomas) promotes tumor invasion and the shift to malignancy.

Gap Junction (Nexus) 

1. Cytoskeletal compartments
2. Major functions
3. medical significance

Communicating junction

1. none
2. Allows direct transfer of small molecules and ions from one cell to another
3. Mutations in various connexin (one of the transmembrane link proteins) genes have been linked to certain types of deafness and peripheral neuropathy

Desmosome (Macula adherens) 

1. Cytoskeletal compartments
2. Major functions
3. medical significance

anchoring junction

1. intermediate filaments (keratins)
2. Provides points of strong intermediate filament coupling between adjacent cells, strengthening the tissue
3. Autoimmunity against desmoglein I leads to dyshesive skin disorders, characterized by reduced cohesion of epidermal cells.

Hemidesmosome

1. Cytoskeletal compartments
2. Major functions
3. medical significance

Anchoring junction

1. intermediate filament
   
2. Anchors cytoskeleton to the basal lamina
3. Mutations in one of the integrin (one of the transmembrane link proteins) gene are linked to some types of epidermolysis bullosa, a skin blistering disorder (Ex. pemphigus vulgaris)

Simple squamous epithelia

1. Examples of distribution
2. Main function

1. lining of vessels (endothelium); serous lining of cavities; peribardium, pleura, peritoneum (mesothelium)
2. Facilitates the movement of the viscera, active transport by pinocytosis, secretion of biologically active molecules, often exhibit transcytosis

Simple cuboidal epithelia

1. Examples of distribution
2. Main function

1. Covering the ovary and thyroid
2. Covering and secretion

Simple columnar epithelia

1. Examples of distribution
2. Main function

1. Lining of intestine and gallbladder
2. Protection, lubrication, absorption, and secretion

Pseudostratified epithelia 

1. Examples of distribution
2. Main function

Layers of cells with nuclei at different levels; not all cells reach surface but all adhere to basal lamina.

1. Lining of trachea, bronchi, nasal cavity
2. Protection and secretion; cilia-mediated transport of particles trapped in mucus out of the air passages

Stratified sqamous keratinized epithelia

1. Examples of distribution
2. Main function

1. Epidermis
2. Protection; prevents water loss

Stratified squamous nonkeratinized epithelia

1. Examples of distribution
2. Main function

1. Mouth, esophagus, larynx, vagina, anal canal
2. Protection and secretion; prevents water loss

Stratified cuboidal epithelia

1. Examples of distribution
2. Main function

1. Sweat glands, and developing ovarian follicles
2. Protection and secretion

Stratified transitional epithelia

1. Examples of distribution
2. Main function

1. Bladder, ureters, renal calyces
2. Protection and distensibility

Stratified columnar epithelia

1. Examples of distribution
2. Main function

1. Conjunctiva (Ex. conjunctiva lining the eyelids, where it is both protective and mucus secreting)
2. Protection (and sometimes secretion)

Common epithelial medical problems of habitual smokers

(medical application of ciliated pseudostratified epithelium of bronchi)

Chronic bronchitis can be seen common among habitual smokers.

For people with chronic bronchitis, the number of goblet cells in the lining of airways in the lungs often increase greatly. This leads to excess production of mucus, and too few numbers of ciliated cells for rapid removal of mucus, contributing to obstruction of airways.

The ciliated pseudostratified epithelium lining the bronchi of smokers can also be transformed into stratified squamous epithelium by metaplasia.

Releases products, usually containing proteins or glycoproteins, by means of exocytosis at the apical end of the secretory cells.

Most exocrine glands, salivary gland, and mammary gland are merocrine.

The products are produced by the disintegration of the secretory cells themselves as they complete their terminal differentiation, which involves becoming filled with product.

Sebaceous glands of hair follicles are best examples of holocrine glands.

Secretion involves loss of membrane-enclosed apical cytoplasm, usually containing one or more lipid droplet.

Can be seen in mammary glands.

Malignant tumors of epithelial origin are called _1_. Malignant tumors derived from glandular epithelial tissue are called _2_.

1. carcinomas
2. adenocarcinomas

What gland is responsible for acne (acne vulgaris)? What causes acne?

Holocrine sebaceous gland

Excessive holocrine secretion of sebum and keratin triggered by the surge of the steroid hormone testosterone that occurs in both genders at puberty frequently blocks the ducts within the gland. Also, activity of the normal commensal skin bacterium Propionibacterium acnes within the blocked duct commonly produces localized inflammation.

A male infertility, or immotile spermatozoa, which is one of the symptoms of immotile cilia syndrome (Kartagener syndrome) is caused by mutation in ___.

Microtubules in cilia and flagella

Exocrine glands producing mucus, or similar individual cells called _1_, are called _2_. Oligosaccharide components of mucus stain well with _3_.

1. goblet cells
2. mucous glands
3. PAS stain

Exocrine glands producing largely enzymes (proteins) are called _1_ and stain darkly with H&E due to the cells' content of _2_ and _3_.

1. seroud glands
2. RER
3. secretory granules