Introduction to Normal Histology

Question 1

Light Microscopy

Answer 1

There is a light source which is used to illuminate the slide. Above the light source is a condenser lens which actually focuses the light on the slide. Above the condenser lens is the specimen (tissue sections). Above the specimen is something called an objective lens. The objective lens magnification can be changed which is then multiplied by a factor of 10 by an eyepiece lens to create a magnification from x10 to x400.

Question 2

Haematoxylin Campechianum

Answer 2

Dye used by the Mayan civilisation for fabrics. When the Spanish came to the new world, the dye became a luxury as fabric of colour was a sense of royalty (haematoxylin was more expensive than gold).

Question 3

Eosin

Answer 3

Developed by a man named Heinrich Currer. He synthesized this from Fluoresceine, which is a naturally occurring substance. He named this due after the woman he fell in love with.

Question 4

Acidic/Basic Dyes

Answer 4

Dyes work by basic combinations. An acidic dye will stain basophilic structures and basic dyes will stain acidic structures. DNA and RNA are basophilic. Proteins are actually more basic so are acidophilic (get stained very easily by an acid dye).

Question 5

Types of Tissue

Answer 5

Nervous tissue: brain, spinal cord and nerves
Muscle tissue: Cardiac muscle, smooth muscle and skeletal muscle
Epithelial tissue: Internal surfaces and skin
Connective tissue: Fat, bone and tendon.

Question 6

Cellular Differentiation

Answer 6

The process by which a less specialised cell type becomes a more specialised cell type.

Question 7

Epithelium

Answer 7

Continuous sheets of cells which line the internal surfaces and cover the external surface of the body.
A selective barrier which protects tissues.
Often involved in absorption and secretion.

Question 8

Epithelial cells

Answer 8

Are highly polarised
The apical domain is the surface that faces the lumen of the organ or the external environment.
The lateral domain faces the adjacent cells.
The basal domain is the surface that attaches to the basement membrane.

Question 9

Types of epithelium

Answer 9

Simple Squamous epithelium
Cuboidal epithelium
Coumnar epithelium
Squamous stratified epithelium
Stratified cuboidal epithelium
Stratified columnar epithelium
Pseudostratified epithelium
Transitional epithelium

Question 10

Simple squamous epithelium

Answer 10

Consists of a single layer of flattened cells. The thinness of these cells facilitates the transfer if materials (e.g. gases, fluids or nutrients) across the epithelium.
Example: the alveoli of the lung are lined by simple squamous epithelium.

Question 11

Simple cuboidal epithelium

Answer 11

Simple cuboidal epithelium consists of a single layer of cuboidal cells. This epithelium is often associated with absorption, secretion, or excretion of waste matter.
Example: the pancreatic ducts are lined by simple cuboidal epithelium.

Question 12

Simple coumnar epithelium

Answer 12

Consists of single layer of cells that are taller than they are wide. This epithelium is often associated with absorption and secretion.
Example: the ileum is lined by simple columnar epithelium.

Question 13

Pseudostratified Columnar Epithelium

Answer 13

Pseudostratified epithelium appears to be stratified because the nuclei of the epithelial cells are at different levels. However, each cell is in contact with the basement membrane, but not all cells reach the lumen.
Example: the trachea is lined by pseudostratified columnar epithelium.

Question 14

Stratified Squamous Epithelium

Answer 14

Stratified squamous epithelium has multiple layers of cells becoming flattened as they move from the basal layer to the apical layers, It provides protection from abrasion and is keratinized on the external surface of the body.
Examples:
Skin is lined by keratinising squamous epithelium.
The oesophagus and ectocervix are lined by non-keratinising squamous epithelium.

Question 15

Layers of the epidermis of the Skin

Answer 15

Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

Question 16

Stratified Columnar Epithelium

Answer 16

An unusual type of epithelium, seen in some ducts from the exocrine glands.
Example: Oesophageal wall.

Question 17

What is the preferred name of transitional epithelium

Answer 17

Urothelium

Question 18

Urothelium (Transitional Epithelium)

Answer 18

This epithelium is adapted for extensibility and is restricted to the urinary tract. It has multiple layers of cells with an outermost layer of much larger, dome-shaped cells (umbrella cells) that change shape during contraction and distention.
Previously called transitional epithelium, but the term urothelium is now preferred.

Question 19

Connective Tissue

Answer 19

Provides support, binds together, and protects tissue and organs of the body.
Comprises cells, protein fibres, and an amorphous ground substance. Together the fibres and ground substances make up the extracellular matrix.
The extracellular matrix is the major component of most connective tissue.

Question 20

Connective Tissue Fibres

Answer 20

Collagen fibres - most are type I collagen (most abundant protein in the body) used for tensile strength (resistance to stretching).
Elastic fibres: contains elastin and fibrillin used for elasticity - can be stretched, yet still, return to its original length.
Reticular fibres - contains type III collagen used for support - network of thin fibres.

Question 21

Fixed cells in connective tissue

Answer 21

Fixed cells are normal components of connective tissue
Fibroblasts produce and maintain the extracellular matrix. They are the most common cell type in connective tissue.
Macrophages are phagocytic cells that engulf and digest microbes, cellular debris, and foreign substances.
Mast cells release molecules that dilate blood vessels and recruit more immune cells to a site of mast cell activation.

Question 22

Transient Cells

Answer 22

Transient cells are leukocytes (white blood cells) that circulate in the bloodstream and migrate into connective tissue at sites of an immune response.

Question 23

Dense Regular Connective Tissue

Answer 23

Composed of type I collagen fibres oriented in the same direction.
Provide tensile strength in one direction
Example: Tendons

Question 24

Dense Irregular Connective Tissue

Answer 24

Contains type I collagen fibres woven in multiple directions.
Provides tensile strength in multiple directions.
Example: the dermis of the skin.

Question 25

Loose (Areolar) Connective Tissue

Answer 25

White fat: Long-term storage of energy
Brown fat: generation of heat (thermogenesis)

Question 26

Skeletal Muscle

Answer 26

Diameter: 10-100 um
Connected to bone (or cartilage) by way of ligaments and produce all movements of parts of the body.
Long cylindrical cells
Multinucleated cells with many peripheral nuclei
Striated muscle - exhibit cross-striations
Voluntary control - innervated by the somatic nervous system (motor neurons)
Responds quickly to stimuli
Satellite cells - skeletal muscle stem cells

Question 27

Cardiac Muscle

Answer 27

Cardiac myocytes have diameter of 10-20um
Short, branched cells that form a syncytium (coupled by a gap junction)
Generally single centrally located nucleus (occasionally binucleate)
Striated muscle - exhibit cross-striations
Intercalated discs join cells end-to-end.
Involuntary control - innervated by the autonomic nervous system
Automatic rhythmic contractions for life.
Long lived cells
Poor capacity for regeneration

Question 28

Smooth muscle

Answer 28

Diameter 3-15 um
Used to apply pressure to organs (such as the stomach, intestines and uterus) and blood vessels.
Spindle-shaped cells of variable size
Single centrally located nucleus
Non-striated muscle
Involuntary control - innervated by the autonomic nervous system
Responds slowly to stimuli and capable of long-time sustained contractions
Retain the ability to divide