Histology Week 1

Question 1

Describe a cell:

Answer 1

The smallest unit of living structure capable of independent existence, composed of a membrane enclosed mass of protoplasm and containing a nucleus. Highly variable and specialized in structure and function, though all must at some stage replicate proteins and nucleic acids, utilize energy and reproduce themselves.

Question 2

Describe an organelle:

Answer 2

One of the specialized parts of a cell; these subcellular units include mitochondria, the Golgi apparatus, nucleus and centrioles, smooth and rough endoplasmic reticulum, vacuoles, lysosomes, plasma membrane, and certain fibrils

Question 3

Which organelles have single membrane: intracellular compartments:

Answer 3

• lysosome - perosisome - rER (rough surface - golgi appartus

Question 4

What structures are bound by two membranes within the cell?

Answer 4

• nucleus - mitochondria

Question 5

Which organelles are not bounded by membranes:

Answer 5

• nucleolus - actin filaments - centrosome - microtuble - free ribosomes

Question 6

H&E stain: Hematoxylin and eosin; describe pink vs blue color stain:

Answer 6

Proteins: pink Basophilic dye: negatively charged (blue/purple) - DNA/RNA/ribosomes

Question 7

What does a pale staining nucleus indicate? What does a dark staining nucleus indicate?

Answer 7

loose packed (euchromatin) more active tightly packed (heterochromatin) less activity

Question 8

Difference between EM and LM?

Answer 8

EM all in black and white and more detailed; LM in color

Question 9

Sketch a typical eukaryotic cell.

Answer 9

see pic

Question 10

Describe Plasma membrane:

Answer 10

acts as a physical barrier to enclose cell contents; regulates material movement into and out of the cell; establishes and maintains an electrical charge difference across the plasma membrane; functions in cell communication • made of phospholipids, cholesterol and proteins • is a lipid bilayer • contains proteins (receptors, pumps, channels) • is not homogeneous in composition

Question 11

Cilia:

Answer 11

short numerous membrane extensions supported by microtubules, which occur on exposed membrane surfaces of some cells. Move substances

Question 12

Microvilli:

Answer 12

Numerous thin membrane folds projecting from the free cell surfaces support by microfilaments. Increases membrane surface area for greater absorption

Question 13

Nucleus:

Answer 13

large enclosed structure with double membrane, contains chromatins, nucleolus and nucleoplasm. Houses DNA that serves as the genetic material for directing protein synth.

Question 14

Nucleolus:

Answer 14

functions in synthesis of ribosomes (initial ribosomal assembly) rRNA

Question 15

Nuclear pores:

Answer 15

opening through the nuclear envelope. portal for substances to enter and leave

Question 16

Ribosomes

Answer 16

structures essential for protein synthesis, composed of RNA and ribosomal proteins. Exit nucleus through nuclear pore. Macromolecular structure and can only be resolved by EM. 50% RNA by mass

Question 17

Cytoskeleton

Answer 17

a system of hollow tubules/filaments and their associated proteins (microfilaments, intermediate filaments, microtubles). Filaments self assemble. Responsible for the cell shape and forms mechanical linkages, movement

Question 18

Microfilament:

Answer 18

actin (protein) filament, found throughout the cytoplasm but concentrated just beneath the plasma membrane in the apical projections named microvilli. Also found in the contractile apparatus of muscle

Question 19

Intermediate filaments:

Answer 19

smaller than microtuble and larger than a microfilament. Made of proteins such as keratins, lamin, GFP. Have different chemical structure and roles in cell func.

Question 20

Microtubles

Answer 20

made of tubulin and numerous accessory proteins. Important for intracellular trafficking of organelles and vesicles. Flagella and cilia contain a microtuble core that is required for mobility.

Question 21

Rough Endoplasmic Reticulum (rough ER):

Answer 21

network of membranes with ribosomes, synthesizes proteins for secretion AND integral membrane proteins of the plasma membrane

Question 22

Smooth Endoplasmic reticulum (smooth ER):

Answer 22

found in cytoplasm, does not contain ribosomes. Synthesizes steroid hormones, detoxifies drugs, synthesizes lipids, glycogen synth and breakdown and storage, calcium storage (muscle contraction)

Question 23

Golgi apparatus:

Answer 23

modifies, packages and sorts materials that arrive from the ER in transport vesicles; forms secretory vesicles and lysomes

Question 24

Lysomes:

Answer 24

major digestive organelles of the cell, single membrane, hydrolytic enzymes to digest components, best identified by histochemical reaction for acid phosphate Lysome storage disease: Tay-sachs, B-hexosaminidase deficiency, primary lysomal hydrolase defect

Question 25

What are the four basic tissue types?

Answer 25

Epithelial, connective, neural and muscle

Question 26

Describe epithelial tissue:

Answer 26

• line cavities and cover surfaces • function is to separate 2 distinct domains while interacting with the contents of each domain. Simple: Squamous (flat), Cuboidal (cube), Columnar (taller\>wide), Pseudostratified Stratified (named from what touches the lumen): Squamous, Cuboidal, Columnar, Transitional

Question 27

Describe muscle tissue:

Answer 27

• specialized for contraction and the production of force. Types: Striated Muscle: Skeletal and cardiac (centrally located nuclei) Smooth muscle: surrounds hollow organs (single nuclei located in the center of the cell)

Question 28

Describe connective tissue:

Answer 28

• composed of cells and extra-cellular matrix • a function is to support and hold things together It can have more cells than fibers. Connective tissue proper: Loose connective tissue & Dense connective tissue (Regular and Irregular (fibers go everywhere) Specialized Connective Tissue: 1. Blood 2. Hematopoietic tissue 3. Lymphatic tissue 4. Cartilage – Module 2 5. Bone – Module 2 6. Adipose tissue – Module 2

Question 29

Describe neural tissue:

Answer 29

• made of neurons and glial cells (supporting cells) • function to sense information • specialized to send signals over long distances at high speed Central Nervous System (CNS): Consists of the brain and spinal cord Peripheral Nervous System (PNS): Consists of cranial, spinal, and peripheral nerves. Collections of nerve cell bodies outside of the CNS (ganglia). Specialized nerve endings (motor and sensory)

Question 30

Define epithelial tissue and differentiate it from the other three basic tissue types

Answer 30

Epithelial tissue: lines cavities and covers surfaces. Its function is to separate 2 distinct domains while interacting with the contents of each domain. (look for large lumen or surface) \* tightly packed (contains contents) \* Form a sheet \* DO NOT contain blood vessels (avascular) \* attached to a basement membrane \* sit on underlying connective tissue \* have polarity (apical interacts with the lumen = drives process, basal interacts with basement and lateral portions)

Question 31

Identify the “faces” of an epithelial cell and list the membrane modifications that may exist on each face.

Answer 31

Apical: - microvilli (increases surface area, has actin filaments and connect into a terminal web connecting it to the cell), brush border - cillia: shorter, with microtubules, motile (present in respiratory tract), anchored by a basal body, wispy appearance Lateral Surface: cell-cell attachment sites, junctional complexes - occluding junctions: (zonula occludens, seals cells together - anchoring junctions: zonula: goes around the entire cell macula (spot weld) - communicating junctions (gap junctions) Basal Surface - Basement membrane a.) basal lamina: type IV collagen -- scaffolding, laminins - cell ECM interactions, proteoglycans - most of the volume, negative b.) reticular lamina: type III collagen c.) function: attachment to underlying tissue, compartmentalization (cancer), filtration, scaffolding for reconstruction - anchoring junctions: hemidesmosome and focal adhesions - basal infoldings: (nucleus will be more apical) allow for increased transport with more mitochondria to supply the energy

Question 32

Occluding junction

Answer 32

tight junctions: seal plasma membrane of adjacent cells together. Formed by transmembrane proteins (ie occludin and claudin). Barrier against paracellular transport. Permeability varies. Lateral domain (goes around the entire cell) - tight junction especially important in the kidney to maintain the concentration being excreted

Question 33

Cilia:

Answer 33

motile structures that can move substances across the epithelial surfaces. It has a core of microtubules. The basal body acts as the organizing center for the cilium

Question 34

Microvilli:

Answer 34

increases surface area of the cell, contain core of actin filaments

Question 35

Anchoring junctions: zonula adherens and Macula Adherens Desmosome:

Answer 35

**zonula adherens:** Provides lateral adhesion between adjacent cells, consists of proteins cell adhesion molecules (CAMS) which link into the cytoskeleton Macula Adherens cadherins from adjacent cells use a calcium-dependent mechanism to span wider intercellular spaces than can the zona occludens. MNEMONIC CADHErins are Calcium-dependent ADHEsion proteins. **Desmosome:** strong spotlike junctions between epithelial cells, has an attachment plaque

Question 36

What's an easy way to remember the order of the cell junctions

Answer 36

ZO, ZA, MA: zona ocluding, zona adherens, macula adherens)

Question 37

Gap junctions:

Answer 37

permits direct passage of molecules from one to another through pores. coordinates activity of adjacents cells, is an accumulation of transmembrane pores and is formed by subunits of connexin protein family. Opens and closes via a conformational change

Question 38

Describe simple epithelia and the various types

Answer 38

Simple epithelia: single layer Simple squamous: cells are flat, like scales (width greater than height Has specific names given location: Endothelium simple squamous epithelium that lines blood and lymph vessels (endo = within) Mesothelium: lines walls and covers the contents of closed cavities of the body (meso = middle) Simple cubodial: cells are like cubes (round nucleus) Simple columnar: cells are taller than they are wide (oval nucleus) Pseudostratified: all cells touch basement membrane but NOT ALL reach the apical surface (respiratory system!)

Question 39

Describe stratified epithelia and the various types

Answer 39

Stratified epithelia: \>1 layers (these are classified by the top layer of the cells!) Stratified squamous epithelium: either keratinized (nuclei are visible in apical layer or non-keratinized Stratified cuboidal (sweat glands!) Stratified columnar Transitional epithelium: a stratified epithelium with “dome cells” (can flatten out when the bladder is full) \*\*Columnar (a lot of the gut); Transitional: predominantly lines the urine tract \*\*

Question 40

What is the function of simple squamous?

Answer 40

frictionless movement of fluids and/or organs, thin barriers for exchange

Question 41

What is the function of simple cubodial?

Answer 41

May just line a conduit but can absorb and/or secrete materials (great example is a sweat gland)

Question 42

What is the function of simple columnar?

Answer 42

absorption and/or secretion

Question 43

What is the function of kerantinized stratified squamous?

Answer 43

protection of dry areas

Question 44

What is the function of non-kerantinized stratified squamous?

Answer 44

protection of moist areas

Question 45

What is the function of stratified columnar?

Answer 45

barrier, conduit

Question 46

What is the function of pseudostratified?

Answer 46

secretion, conduit in resp tract; movemucus, absorption, conduit in epididymis

Question 47

What is the function of transitional?

Answer 47

A barrier in chamber and tubes that distend