Unit 2: Histology

Question 1

Histology

Answer 1

The study of tissues and their cellular components. It is used in the recognition of pathology and in the discovery of how abnormal biochemical and physiological processes result in disease.

Question 2

Morphology

Answer 2

The examination of cellular arrangements and organization to examine organ structure in terms of form and function.

Question 3

4 major groups of tissues

Answer 3

Connective, epithelium, muscle, and nervous

Question 4

Epithelium

Answer 4

Found covering and lining the surfaces of the body and organs.

Structure: sheets of closely packed cells

Function: protection, exchange, secretion

Question 5

Connective tissue

Answer 5

It’s major function is to hold tissues together. Some have a generalized role in supporting and protecting organs while others have specialized functions (bones provide muscle attachment, blood facilitate the transport of nutrients and removal of wastes).

Structure: spare cells in extracellular matrix

Function: binding and support of other tissues

Question 6

Muscle tissue

Answer 6

Unique property of being able to move when cells contract. 3 types of muscles:

Skeletal - permits movement of the body
Cardiac - moves blood around the vasculature

Structure: long cells (fingers) with contractile proteins.

Function: movement of body parts
Smooth - facilitates movement of food along the alimentary canal.

Question 7

Nervous tissue

Answer 7

Highly complex (especially in the brain)

Structure: neurons with branching extensions

Function: transmission of nerve signals

Question 8

Steps for preparation of specimens for study by standard light microscopy

Answer 8

1. Obtaining a sample with the proper orientation
2. Fixing or preserving the specimen
3. Sectioning the specimen into thin slices
4. Staining the specimen for visualization
5. Microscopic examination of the specimen

Question 9

Orientation

Answer 9

First step in light microscopy; orientation helps to visualize the morphology of a structure. This is because improper orientation may cause the tissue to become damaged during later stages of preparation. Most tissues are embedded flat with a margin of embedding medium surrounding them for support. During sectioning the tissue should be oriented in a way that results in least resistance to the knife.

Question 10

Tubular structures

Answer 10

Tissue that may require a specific orientation in light microscopy preparation; structures with tubular morphology (sweat gland ducts or blood vessels) are usually cut to display the cross-section of the lumen.

Question 11

Epithelial Biopsies

Answer 11

Biopsies of epithelia, such as the skin or the intestines, are cut in a plane at right angles to the surface, and oriented in a certain way so that the knife cuts from the basement membrane through to the apical epithelial membrane. This way, compression and distortion of the epithelial surface is minimized.

Question 12

Muscle Biopsies

Answer 12

Sections of muscle may be cut in transverse or longitudinal planes.

Question 13

Multiple tissue samples

Answer 13

To facilitate comparison, multiple tissue samples are oriented similarly, side by side, with, for example, the apical epithelial surfaces all facing in the same direction.

Question 14

Fixation

Answer 14

Second step of tissue preparation; helps to prevent the specimen from undergoing physiological changes. Also helps to deactivate internal enzymes within cells to prevent degradation from within. Can also help to increase the mechanical strength of tissue and reduce the growth of microbe colonies.

Question 15

Methods of fixation

Answer 15

Chemical perfusion, heat fixation, etc.

Question 16

Embedding

Answer 16

Third step in light microscopy preparation; Embedding involves the following: correctly oriented specimens are fixed and encased within a suitable medium, providing them with elasticity and ensuring they are supported during sectioning and subsequent analysis.

Question 17

Paraffin wax embedding

Answer 17

The standard method for the preparation of finely sectioned specimens for histological analysis by microscopy. Paraffin wax fills the tissue, supporting all cellular components and resisting distortion during sectioning.

Question 18

Frozen sections

Answer 18

Alternative to paraffin wax because the wax can be too damaging or time consuming. Specimens are rapidly frozen by immersion in liquid nitrogen so that the tissue hardens into a solid mass.

Question 19

Sectioning

Answer 19

Fourth step in light microscopy preparation; the slicing of embedded specimen using a microtome and attachment to a surface (usually a slide) for analysis under a microscope.

Question 20

Stains

Answer 20

Fifth step in light microscopy preparation; Staining is require to see the colorless cell.

Question 21

Methyl blue

Answer 21

Stain widely used in differential staining of tissue sections, where more than one chemical stain is used, such as trichrome staining.

It stains collagen blue.

Question 22

Hematoxylin and eosin (H&E)

Answer 22

Staining is used to differentiate nucleic acids in the nucleus from basic proteins within the cytoplasm.

Cell nuclei stain purple/black (hematoxylin) and most components of the cell cytoplasm stain pink/red (eosin).

Question 23

van Gieson

Answer 23

This stain is used for general staining of connective tissue fibers.

Collagen fibers stain pinkish-red, muscle stains yellow, and elastic fibers stain brown-black.

Question 24

Trichrome

Answer 24

This method uses three different dyes to differentially stain cellular components. One of these is often methyl blue.

Question 25

SIlver nitrate

Answer 25

Silver nitrate solution can be used to stain tissues in several different ways. One method, called Golgi's method, selectively stains the entirety of some neurons black, thus revealing their cellular architecture. A different technique can be used to highlight reticular fibers.

Question 26

Immunohistochemical methods

Answer 26

utilizes a different approach to visualize cellular contents: rather than dyes, it exploits the highly specific interaction between antibody and antigen to allow precise identification, localization, and in some cases, quantification, of cellular proteins, such as receptors or enzymes.

Question 27

Light (optical) microscope

Answer 27

How does it work: Uses beams of visible wavelengths of light, focused through glass lenses, to produce magnified images. Magnification: Up to 2000x. Lens: Glass. Uses: ability to view color, relatively low cost makes this device more popular in education and medical sectors. Stains used: those highlighting tissue/cellular components in different colors. Chromatic dyes used. Disadvantages: limited magnification and depth field. Types: simple (one lens), compound (many lenses), and digital light microscope.

Question 28

Electron microscope

Answer 28

How does it work: Uses particle beams of electrons, focused through magnetic lenses and metal apertures, to produce highly magnified 2D and 3D images. Magnification: up to 2000000x Lens: electrostatic/electromagnetic Uses: Used to visualize smaller structures not visible by light microscopy. Allows 3D visualization of structures. Is used in observation of dry, fixed specimens of micro-organisms, cells, large molecules, biopsy samples, metals, and crystals etc. Stains used: Stains highlight tissue by increasing electron absorption. Electron-dense heavy metals often used. Disadvantages: Expensive to build, maintain, and run. Very sensitive to vibrations and external magnetic currents. More elaborate preparation of specimens often needed and specimens must be dry. Not possible to observe living specimens or color. Types: Transmission electron microscope (TEM) for 2D images, and scanning electron microscope (SEM) for 3D images.

Question 29

Characteristics of epithelial tissues

Answer 29

Avascular (no blood cells entering between the cells. The cells are maintained via blood vessels lying deep within the basement membrane. Highly cellular with little extracellular material. High regenerative capacity

Question 30

Functions of epithelial tissue

Answer 30

Selective absorptive barriers regulating the movement of substances into and out of the body. Secretory surfaces, comprising the functional units of glandular secretion. Protective surfaces, such as the skin.

Question 31

What is the classification of covering and lining epithelium based on?

Answer 31

The three-dimensional shape of the epithelial cells comprising it, as observed by light microscopy. The way in which the epithelial cells are arranged into layers.

Question 32

Squamos

Answer 32

Epithelial cell; flat, plate-like cells

Question 33

Cuboidal

Answer 33

Epithelial cell; cube-like cells.

Question 34

Columnar

Answer 34

Epithelial cell; column-shaped cells. Greater height than width.

Question 35

Transitional

Answer 35

Epithelial cell; cuboidal or columnar can change shape during stretching and compression.

Question 36

Simple Epithelium

Answer 36

A single layer of cells.

Question 37

Stratified Epithelium

Answer 37

Multiple layers of cells.

Question 38

Pseudostratified Epithelium

Answer 38

Cells appear to be arranged in layers, but careful observation reveals that all cells are anchored to the underlying basement membrane.

Question 39

Simple Squamous Epithelium

Answer 39

Function: Diffusion and filtration. Locations: Capillary networks surrounding the alveoli in the lungs. Lines the heart and blood and lymphatic vessels. Component of serous membranes. composed of a single layer of flat epithelial cells, each containing a flattened, centrally located nucleus.

Question 40

Endothelium

Answer 40

the simple, squamous epithelium lining the heart, blood vessels, and lymphatic vessels. In capillaries, the endothelial cells act as a selective barrier, permitting various substances to move from the blood into the interstitial fluid.

Question 41

Mesothelium

Answer 41

simple, squamous epithelium but it has a different embryological origin to endothelium. Mesothelium constitutes the epithelial layer of serous membranes, such as the pericardium, pleura, and peritoneum.

Question 42

Simple Cuboidal Epithelium

Answer 42

Function: secretion and absorption. Locations: Proximal and distal convoluted tubules of the kidney and thyroid gland. made up of a single layer of approximately cube-shaped epithelial cells, each containing a spherical, centrally located nucleus.

Question 43

Simple columnar epithelium

Answer 43

Simple columnar epithelium consists of a single layer of column-shaped epithelial cells, each with an oval nucleus near its base.

Question 44

Non-ciliated simple columnar epithelium

Answer 44

made up of simple columnar epithelial cells which often have microvilli at their apical surface. Interspersed between these columnar cells are goblet cells, which are specialized epithelial cells that secrete mucus at their apical surface. Microvilli increases SA and mucus lubricates and protects. Line functional tracts; small intestine and the gall bladder.

Question 45

Ciliated simple columnar epithelium

Answer 45

Ciliated simple columnar epithelium is made up of simple columnar epithelial cells with cilia at their apical surface. The ciliated columnar cells are interspersed with mucus-secreting goblet cells. Function: removes foreign particles. Lining of the uterine tubes, where the beating of the cilia is responsible for the movement of the egg from the ovary to the uterus. And auditory tubes.

Question 46

Keratinized stratified squamous

Answer 46

Function: Protects the body from heat, microbes, and damaging substances. Locations: Forms superficial layer of the skin. Contains protein keratin which is a waterproof layer that can dehydrate cells.

Question 47

Non-keratinized stratified squamous

Answer 47

Function: Protects the body against microbes. Locations: Forms moist linings such as the buccal cavity, esophagus, and part of the cervix.

Question 48

Stratified Cuboidal

Answer 48

Function: protection, secretion, and absorption. Locations: Makes up part of the sweat glands, mammary glands, and salivary glands.

Question 49

Stratified columnar

Answer 49

Function: Protection and secretion. Locations: Ocular conjunctiva of the eye. Ducts of larger salivary glands.

Question 50

Transitional Epithelium

Answer 50

Function: Forms stretchable lining Locations: lines tissues that expand and contract, such as the urinary bladder.

Question 51

Exocrine glands

Answer 51

consist of a glandular portion, and a duct portion. They secrete their non-hormone products into ducts that carry these products to other organs or outside the body ex. sweat glands, goblet cells, digestive glands, and sebaceous glands.

Question 52

Endocrine glands

Answer 52

lack ducts. They produce hormones which are secreted directly into the bloodstream Ex. thyroid, parathyroid, pineal, pituitary, and suprarenal glands.

Question 53

Exocrine glands and secretion types

Answer 53

Merocrine - sweat glands, salivary glands, pancreatic aciner glands; most common gland Apocrine - mammary glands Holocrine - sebaceous/oil glands

Question 54

Connective tissue

Answer 54

The most widespread, and the most varied of all tissues. It is the collective term for support cells and associated extracellular matrix.

Question 55

Characteristics of support cells

Answer 55

1. They are derived from embryonic cells called mesenchymal cells. 2. They start life as immature blast cells capable of cell division and secretion of extracellular matrix. 3. They produce most of their extracellular matrix materials before differentiation into mature cyte cells. 4. In their mature form, they sit within their matrix, forming sparsely cellular connective tissues, where they continue to maintain the matrix. 5. They adhere to their extracellular matrix materials, rather than adjacent cells.

Question 56

Examples of support cells

Answer 56

fibroblasts, adiipocytes, chondroblasts, osteoblasts, and myofibroblasts

Question 57

Fibroblasts

Answer 57

large, flat, branching cells present in most connective tissue. They secrete fibers including collagen, and some of the ground substance component of the extracellular matrix

Question 58

Adipocytes

Answer 58

(fat cells) are highly specialized support cells that store lipids which can be metabolized to provide energy. They are present under the skin and surrounding various organs, where they also function as protective padding.

Question 59

Chondroblasts

Answer 59

small, rounded cells with small nuclei, and are found in cartilage, where they secrete components of the extracellular matrix.

Question 60

Osteoblasts

Answer 60

mononucleate cells that secrete the extracellular matrix components of bone.

Question 61

Myofibroblasts

Answer 61

differentiated fibroblasts committed to becoming smooth muscle cells. They have contractile properties and also secrete extracellular matrix components.

Question 62

Cells present in connective tissue whose primary function is not support

Answer 62

Mast cells - located near blood vessels supplying tissues primarily. Store and secrete histamine and heparin in response to inflammatory processes and allergic reactions. White blood cells - migrate from blood to connective tissue during times of need. Include macrophages and lymphocytes (plasma cells).

Question 63

Extracellular matrix

Answer 63

made up of fibers (fibrillary proteins) and a ground substance component.

Question 64

Fibers

Answer 64

provide different tensile properties, giving essential strength and support to connective tissue and providing anchorage to their cellular components.

Question 65

3 main types of fibers in extracellular matrix of connective tissue

Answer 65

Collagen fiber - strong and flexible occurring in parallel bundles. Made up of protein collagen. Elastic fibers - small in diameter and branch to form networks of strong, stretchable, interconnected fibers. The main component of elastic fibers is the protein elastin. Reticular fibers - very fine, and branch to form strong, supportive frameworks. Produced by fibroblasts, made up of collagen, and are strengthened/stabilized by a glycoprotein coating. They are present in blood vessel walls, areolar connective tissue, adipose tissue, smooth muscle tissue, and soft organs (spleen and lymph nodes).

Question 66

What does mature connective tissue include?

Answer 66

Loose connective tissue, dense connective tissue, cartilage, bone, and liquid connective tissue.

Question 67

Loose connective tissue

Answer 67

Consists of loosely arranged fibers that form a network btwn cells. Under the skin.

Question 68

Types of connective tissues

Answer 68

Areolar, adipose, and reticular.

Question 69

Dense connective tissue

Answer 69

consists of uniformly arranged, parallel bundles of collagen fibers. It is strong and pliable, but withstands stretching only in the direction of the fibers. Fibroblasts are arranged in rows between the collagen fibers and they secrete both ground substance and fiber components of the tissue. It is poorly vascularized. Tendons and ligaments.

Question 70

Characteristics of loose connective tissue

Answer 70

- Loose connective tissue is a type of connective tissue that surrounds blood vessels, nerves, and organs, holding the epithelium and organs in place. - Consists of many cells - Mainly contains fibroblasts - Consists of loosely arranged fibers - Major function is to serve as a supporting matrix for the blood vessels, lymphatic vessels, nerves, muscle fibers, organs, and the skin.

Question 71

Characteristics of dense connective tissue

Answer 71

- Contains numerous collagen fibers and provides a strong connection btwn tissues that mainly form the structural parts of the body - Consists of fewer cells. - Mainly contain fibrocytes. - Consists of numerous thick fibers. - Produces tendon and ligaments by forming strong, rope-like structures.

Question 72

Types of dense connective tissue

Answer 72

Dense regular connective tissue Dense irregular connective tissue Elastic connective tissue

Question 73

Hyaline cartilage

Answer 73

Function: flexibility, support, friction, reduction, and shock absorption. Location: Temporary skeleton in the fetus. Epiphyseal plates of growing long bones. Articular surfaces of joints and supporting rings in the respiratory passage.

Question 74

Fibrocartilage

Answer 74

Function: strength and rigidity. ``` Location: Intervertebral discs. Tendon attachment to bones. Junctions between flat bones of the pelvis. Menisci of the knee. ```

Question 75

Elastic cartilage

Answer 75

Function: strength, elasticity, and maintenance of shape. Location: Auricle of the ear. Walls of the external auditory meatus and Eustachian tubes. Epiglottis of the larynx.

Question 76

Adipose tissue

Answer 76

Loose connective tissue; fatty tissue, main functions are to store the energy, protect the organs and contribute to the endocrine profile of the body.

Question 77

Reticular tissue

Answer 77

Loose connective tissue; forms a scaffolding for other cells in several organs, such as lymph nodes and bone marrow.

Question 78

Areolar tissue

Answer 78

Loose connective; holds organs in place and attaches epithelial tissue to other underlying tissues. It also serves as a reservoir of water and salts for surrounding tissues.

Question 79

Muscle tissue

Answer 79

A specialized tissue with both contractile and conducing properties. It consists of elongated cells that contract in response to stimulation.

Question 80

3 types of muscle tissues

Answer 80

Cardiac, skeletal, and smooth

Question 81

Skeletal muscle tissue

Answer 81

Structure: Long thin cylindrical striated fibers. Many peripheral nuclei. Location: attached to bones of the skeleton via tendons. Function: voluntary movement. Maintenance of posture. Protection and production of heat.

Question 82

Cardiac muscle tissue

Answer 82

Structure: branched striated fibers connected via intercalated discs. One or two central nuclei. Location: make up the muscular component of the heart. Function: form the muscular wall of the heart. Contraction of the heart muscle for distribution of blood around the body.

Question 83

Smooth muscle tissue

Answer 83

Structure: spindle shaped non-striated fibers, one central nucleus. Location: blood vessel walls. Iris of the eye. Airways to the lung. Walls of the stomach, intestines, gallbladder, urinary bladder, and female uterus. Function: constriction of vessels, airways, and tracks for movement of substances through them. Contraction of organ walls for expulsion of content.

Question 84

Nervous tissue

Answer 84

has a high degree of excitability and conductivity – more than other tissues. Found in brain, spinal cord and nerves.

Question 85

What types of cells make up nerve tissue?

Answer 85

Neurons (nerve cells): the units that conduct nervous impulses. Neuroglia (a specialized group of support cells) – non-neuronal cells. Protect and assist neurons.

Question 86

Two main types of membrane

Answer 86

Epithelial (mucous membranes, serous membranes, or cutaneous membranes. Consisting of an epithelium overlying a connective tissue layer). and synovial (exclusively of connective tissue and are found lining the cavities of mobile joints).

Question 87

Mucous membrane

Answer 87

found lining body cavities, or tracts, that open into the external environment, such as the digestive, respiratory, and reproductive tracts.

Question 88

Serous membrane

Answer 88

also known as serosae, are found covering organs (visceral serous membrane) and lining body cavities (parietal serous membrane) that do not open into the external environment.

Question 89

Cutaneous membrane

Answer 89

refers to the skin covering the surface of the body.

Question 90

Cutaneous membrane - dermis layer

Answer 90

Connective tissue layer (dermis) consists of areolar connective tissue and dense irregular tissue. It lies deep to the epithelial layer, supporting it and anchoring it to underlying structures.

Question 91

Synovial membranes

Answer 91

Line joint cavities and produce the fluid within the joint.

Question 92

Gliosis

Answer 92

the most common response to the damage of nervous tissue. It is the formation of scar tissue composed of astrocyte glial cells.

Question 93

What is bone

Answer 93

A rigid connective tissue that contains calcium and phosphorus.

Question 94

Keloid

Answer 94

The result of excess production of collagen in the formation of a scar.

Question 95

Myelin

Answer 95

The fatty insulation material that covers and protects some nerve fibers.

Question 96

Myocradium

Answer 96

Thick, muscular layer of the heart wall.