GEN HISTO LONG QUIZ (OFFICIAL)

Histology

● Study of the tissues of the body and how these tissues are arranged to constitute organs
● Dependent on the use of the microscope and other molecular methods of study

Light Microscopy

● Bright–field Light Microscopy
● Other specialized applications:
fluorescence, phase

Stained tissue

This is examined with ordinary light passing through the preparation

FLUORESCENCE MICROSCOPY

Uses UV light, under which only fluorescent molecules are visible, allowing localization of fluorescent probes which can bemuch more specific than routine stain

PHASE-CONTRAST MICROSCOPY

Uses the differences in refractive index of various natural cell and tissue components to produce an image without staining, allowing observation of living cells

CONFOCAL MICROSCOPY

Involves scanning the specimen at successive focal planes with a focused light beam, often from a laser, and produces a 3D reconstruction from the images

Electron Microscopy

● Transmission and scanning electron microscopy

● Based on the interaction of tissue components with beams of electrons

Transmission Electron Microscope

a beam of electrons focused using electromagnetic “lenses” passes through the tissue section to produce an image with black, white, and intermediate shades of gray regions.

Scanning Electron Microscope

beam of electrons does not pass through the tissue section, instead, (1)the surface of the specimen coated with a very thin layer of heavy metal (ie, gold) reflects electrons in a beam scanning the specimen and (2)the reflected electrons are captured by a detector, producing signals that are processed to (3)produce a black -and-white, 3D image.

● Fixation
● Dehydration
● Clearing
● Infiltration
● Embedding
● Trimming

Preparation of Tissues for Study

Small pieces of tissue are placed in solutions of chemicals that cross–link proteins and inactivate degradative enzymes, which preserve cell and tissue structure

What is the process of Fixation?

The tissue is transferred through a series of increasingly concentrated alcohol solutions, ending in 100%, which removes all water.

What is the process of Dehydration

Alcohol is removed in organic solvents in which both alcohol and paraffin are miscible

What is the process of clearing?

The tissue is then placed in melted paraffin until it becomes completely infiltrated with this substance

What is the process of Infiltration?

The paraffin–infiltrated tissue is placed in a small mold with melted paraffin and allowed to harden

What is the process of Embedding?

The resulting paraffin block is trimmed to expose the tissue for sectioning (slicing) on a microtome

What is the process of trimming?

Staining

Process of applying dyes on the tissue sections to see and study the architectural pattern of the tissue and the physical characteristics of cells

1. Hematoxylin
2. Eosin in H&E Staining

staining is facilitated by two contrasting dyes

Hematoxylin

it stains acidic structures blue

Eosin

it stains basic structures pink

Cell

it is the basic living component of the human body

Eukaryotic cells

these are enveloped by a plasma membrane and have a membrane–bound nucleus surrounded by a cytoplasm

Organelles

are the metabolically active units of the cell “little organs”

CELL

Basic structural and functional unit of life

Cytoplasm

structural and fluid components

Nucleoplasm

nuclear envelope, nucleus

PHOSPHOLIPID BILAYER

Cell Membrane Consists of an inner and an outer leaflet known as the?

\

Hydrophobic

non polar fatty acid

Cell Membrane

• Maintains the cell's structural and functional integrity

Cell Membrane

• Acts as a semipermeable membrane
• Assists in cellular recognition and communication
• Maintains a potential difference between the cytoplasmic and extracellular sides

Cell Membrane Fluid Mosaic Model

what is a model of a cell membrane?

CHOLESTEROL

● Present in both leaflets
● Helps maintain the structural integrity
of the membrane
● Affects fluidity of the membrane
○ An increase in cholesterol content decreases membrane fluidity

\

○ Head: faces membrane surface
○ Tail: projects into the interior of the membrane

two leaflets asymmetrically distributed

Head

faces membrane surface

Tail

projects into the interior of the membrane

MEMBRANE PROTEINS

● Major constituent of the membrane (~50% by weight)

Integral Proteins

incorporated directly within the lipid bilayer

Peripheral Proteins

bound to one of the two membrane surfaces

● Amphipathic molecules

it consisting of
polar (hydrophilic) head and two nonpolar (hydrophobic) fatty acid tails

● Decreased saturation of fatty acids
● Decreased length of fatty acids
● Decreased membrane cholesterol content

● Increased temperature in the membrane fluidity causes?

GLYCOCALYX

● Located on the outer surface of the outer leaflet of the plasma membrane
● Consist of polar oligosaccharide side chains and proteoglycans

plasma membrane

● the site where materials are exchanged between the cell and its environment
● It is freely permeable to small, lipid

PASSIVE TRANSPORT

● Movement of substances down a concentration gradient due to the kinetic energy of the substance
● No expenditure of cellular energy is required
● Continues until equilibrium is reached

● Simple Diffusion
● Facilitated Diffusion
● Osmosis

3 PASSIVE TRANSPORT MECHANISMS

SIMPLE DIFFUSION

● Unassisted net movement of small, nonpolar substances down their concentration gradient across a selectively permeable membrane

FACILITATED DIFFUSION

● Movement of ions and small, polar molecules down their concentration gradient
● Assisted across a selectively permeable membrane by a transport protein
● May be channel–mediated or carrier–mediated

OSMOSIS

● Diffusion of water across a selectively permeable membrane
● Direction is determined by relative solute concentrations
● Continues until equilibrium is reached

ACTIVE TRANSPORT

● Transport of ions or small molecules across the membrane against a concentration gradient
● Movement of substances requires expenditure of cellular energy

● Primary Active Transport
● Secondary Active Transport

ACTIVE TRANSPORT MECHANISMS

PRIMARY ACTIVE TRANSPORT

● Movement of substance up its concentration gradient
● Powered directly by ATP

SECONDARY ACTIVE TRANSPORT

● Movement of a substance up its concentration gradient is powered by harnessing the movement of a second substance (eg, Na+) down its concentration gradient

VESICULAR TRANSPORT

● Vesicle formed or lost as material is brought into a cell or released from a cell

● Exocytosis
● Endocytosis
● Phagocytosis
● Pinocytosis
● Receptor–mediated
endocytosis

VESICULAR TRANSPORT MECHANISMS

EXOCYTOSIS

Bulk movement of substance out of the cell by fusion of secretory vesicles with the plasma membrane

ENDOCYTOSIS

Bulk movement of substances into the cell by vesicles forming at the plasma membrane

PHAGOCYTOSIS

Particulate materials external to the cell are engulfed by pseudopodia

PINOCYTOSIS

Cell membrane forms similar folds or invaginates to create a pit containing a drop of extracellular fluid

RECEPTOR–MEDIATED ENDOCYTOSIS

Receptors bind specific molecules (ligands) and then taken up by the cell

● Organelles
● Inclusions
● Cytoskeleton

3 CYTOPLASMIC STRUCTURAL COMPONENTS

RIBOSOMES

STRUCTURE:
● Nonmembranous organelles (12 nm wide and 25 nm long)
● Consist of a small and a large subunit

RIBOSOMES

(1) It is Located free in the cytosol
(2) Bound to membranes of the rough endoplasmic reticulum (RER)
(3) Attached to the cytoplasmic surface of the outer nuclear membrane

RIBOSOME

Its function is PROTEIN SYNTHESIS

1. BOUND RIBOSOMES
2. FREE RIBOSOMES

Protein synthesis have 2 ribosomes

Bound Ribosomes

produce proteins that are secreted, incorporated into plasma membrane, and within lysosomes

Free Ribosomes

produce proteins used within the cell

ROUGH ENDOPLASMIC RETICULUM

● Its structure include System of membrane–bounded sacs, or narrow tubules whose outer surface is studded with ribosomes
● Extends from the surface of the nucleus throughout most of the cytoplasm and encloses a series of intercommunicating channels

cisternae

a series of intercommunicating channels enclosed by RER

ROUGH ENDOPLASMIC RETICULUM

Its function is to Synthesizes proteins for secretion, incorporation into the plasma, membrane, and as enzymes within lysosomes

SMOOTH ENDOPLASMIC RETICULUM

Its structure is Irregular network of membrane–bounded channels that lack ribosomes on its surface

SMOOTH ENDOPLASMIC RETICULUM

Its function are the ff:
(1) Lipid biosynthesis,
(2) Detoxification of potentially harmful compounds, and
(3) Sequestration of Ca++ ions

GOLGI APPARATUS

STRUCTURE:
Several membrane–bounded cisternae (saccules) arranged in a stack and positioned and held in place by microtubules

GOLGI APPARATUS

FUNCTION:
Synthesizes carbohydrates, processes membrane–packaged proteins synthesized in the RER, and also recycles and redistributes membranes

————————————————————————
● Cis Face

contains the vesicular tubercular cluster (VTC)

vesicular–tubular clusters (VTC)

which receives transport vesicles from the transitional element of the RER

● Medial Compartment

between the cis and trans faces

● Trans Face

associated with vacuoles and secretory granules

● Trans–Golgi Network (TGN)

it sorts proteins for their final destinations

MITOCHONDRIA

STRUCTURE:
● Rod–shaped organelles
● Possess an outer membrane that surrounds the organelle and an inner membrane, rich in cardiolipin.
● With arrays of enzymes specialized for aerobic respiration and production of adenosine triphosphate (ATP)

cardiolipin

it invaginates to form cristae

MITOCHONDRIA

FUNCTION:
Synthesize most ATP during aerobic cellular respiration by digestion of fuel molecules (eg, glucose) in the presence of oxygen

LYSOSOMES

STRUCTURE:
● Spherical–shaped membrane–bound organelles formed from the Golgi apparatus
● Contain digestive enzymes

LYSOSOMES

FUNCTION:
Digest microbes or materials (eg, ingested by the cell, worn

PEROXISOMES

STRUCTURE:
● Membrane–bound, spherical, or ovoid organelles
● Characterized by the presence of the enzyme catalase
● May contain a nucleoid (absent in human cells), a crystalline core consisting of urate oxidase (uricase).

PEROXISOMES

FUNCTION:
Detoxify specific harmful substances either produced by the cell or taken into the cell; engage in beta oxidation of fatty acids to acetyl CoA

INCLUSIONS

● __Accumulated metabolites__ or other substances that have little or no metabolic activity
● Most are transitory structures not enclosed by a membrane

● Lipid droplets
● Glycogen granules
● Melanin
● Lipofuscin

MOST COMMON INCLUSIONS

Cytoskeleton

○ microtubules 25 nm in diameter;

○ actin filaments or microfilaments (5-7 nm); and

○ intermediate filaments (8

CYTOSKELETON

● Determine the shapes of cells, play an important role in the movement of organelles and cytoplasmic vesicles, and also allow the movement of entire cells

MICROTUBULES

STRUCTURE:
● Straight, hollow tubules (25 nm in diameter) composed of tubulin (𝛂 and 𝛃 tubulin)
● Exhibit polarity

MICROTUBULES

FUNCTION:
● Maintains cell shape and polarity
● Provide tracks for organelle and chromosome movement
● Move cilia and flagella
Microfilaments.

DYNAMIC INSTABILITY OF MICROTUBULES

● Exhibit continuous cycles of polymerization and depolymerization at steady

MICROFILAMENTS (ACTIN FILAMENTS)

STRUCTURE:
● Composed of globular actin monomers (G actin) linked into a double helix (F actin)
● Thin, flexible, and abundant in cells
● Exhibitpolarity

MICROFILAMENTS (ACTIN FILAMENTS)

FUNCTION:
● Contract and move cells; change cell shape; cytokinesis; cytoplasmic transport and streaming

TREADMILLING

● Assembly of actin filaments (F–actin) is polarized
● G–actin subunits added to the plus (+) end and removed at the minus (–) end
● Assembly and disassembly of subunits are promoted by profilin and cofilin

INTERMEDIATE FILAMENTS

STRUCTURE:
● Cable of four intertwined protofibrils, each consisting of bundled tetramers associated end–to–end

INTERMEDIATE FILAMENTS

FUNCTION:
● Strengthen cell and tissue structure; maintain cell shape; maintain nuclear shape (lamins)

Keratin, Vimentin, Neurofilament, Lamins

IMPORTANT INTERMEDIATE FILAMENTS:

NUCLEUS

STRUCTURE:
● Largest organelle of the cell
● Includes the nuclear envelope, nucleolus,
nucleoplasm, and chromatin

NUCLEUS

FUNCTION:
Houses the DNA that serves as the genetic material for directing protein synthesis; produces ribosomal subunits

NUCLEAR ENVELOPE

● Surrounds the nuclear material and consists of two concentric membranes separated from each other by a narrow perinuclear cisterna
● Membranes fuse at intervals, forming openings called nuclear pores in the nuclear envelope

Inner Nuclear Membrane