1What are the four basic types of tissues?
Epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
2What is a tissue?
A group of cells that usually have common characteristics in development and function and work together to carry out specialized activities.
3What is epithelium?
An avascular tissue composed of cells that cover exterior body surfaces and line internal closed cavities and body tubes communicating with the exterior.
4What are the main factors used to classify surface epithelium?
The number of cell layers and the shape of the surface cells.
5What is simple epithelium?
Epithelium that has only one cell layer.
6What is stratified epithelium?
Epithelium that has two or more cell layers.
7How is the shape of surface epithelium classified?
As squamous, cuboidal, or columnar according to the shape of the surface cells.
8What characterises squamous epithelium?
The width of the cell is greater than its height.
9What characterises cuboidal epithelium?
The width, depth, and height are approximately the same.
10What characterises columnar epithelium?
The height of the cell is approximately twice its width.
11What is low columnar epithelium?
Epithelium in which the cell height only slightly exceeds its other dimensions.
12What is pseudostratified epithelium?
A simple epithelium that appears stratified because some cells do not reach the free surface, although the cells rest on the basement membrane.
13What is transitional epithelium or urothelium?
A stratified epithelium with special morphological features that allow it to distend.
14What are the main structural characteristics of epithelium?
It is a cellular sheet of one or many layers; cells are closely adherent through junctional complexes; there is very little intercellular material; and the deep surface rests on a basement membrane.
15What separates epithelium from vascular connective tissue?
The basement membrane.
16What are the two components of the basement membrane?
Basal lamina and reticular lamina.
17Which tissue produces the basal lamina?
Epithelium.
18Which tissue produces the reticular lamina?
Connective tissue.
19Where is the superficial surface of epithelium exposed?
To air or fluid.
20Are blood vessels present within epithelium?
No, epithelium has no blood vessels.
21Are lymph vessels present within epithelium?
No, epithelium has no lymph vessels.
22How is epithelium nourished?
By diffusion from the adjacent supporting tissues.
23What is a major property of epithelial regeneration?
Epithelium has good regenerative capacity.
24From how many germ layers can epithelium be derived?
All three germ layers: ectoderm, endoderm, and mesoderm.
25Which germ layer gives rise to the skin epithelium?
Ectoderm.
26Which germ layer gives rise to the respiratory and digestive system epithelium?
Endoderm.
27Which germ layer gives rise to the cardiovascular system epithelium?
Mesoderm.
28What are the functions of epithelium?
Protection, absorption, secretion, excretion, lubrication, sensation, and reproduction.
29Where does epithelium occur in relation to body surfaces and cavities?
It covers exterior body surfaces and lines internal closed cavities and body tubes communicating with the exterior.
30Which body tubes communicating with the exterior are lined by epithelium according to the lecture?
Alimentary, respiratory, and genitourinary tracts.
31What is the traditional classification of surface epithelium based on?
The number of cell layers and the shape of the surface cells.
32What are the two main categories based on number of layers?
Simple epithelium and stratified epithelium.
33What is the microscopic appearance of simple squamous epithelium?
Thin, plate-like cells closely adhering to the underlying connective tissue surface and appearing mosaic-like on the surface.
34What is characteristic of the cell boundaries in simple squamous epithelium?
They appear interdigitated in a sinuous pattern.
35What is the position and shape of the nucleus in simple squamous epithelium?
A centrally placed ovoid nucleus that produces a bulge in the centre of the cell.
36List the examples of simple squamous epithelium given in the lecture.
Alveolar lining of the lungs; thin limb of Henle’s loop; endothelial lining of blood and lymph vessels; inner surface of the tympanic membrane and membranous labyrinth of the ear; mesothelial lining of serous cavities.
37What type of epithelium lines the alveoli according to the lecture?
Simple squamous epithelium.
38What type of epithelium lines the thin limb of Henle’s loop?
Simple squamous epithelium.
39What type of epithelium forms the endothelial lining of blood and lymph vessels?
Simple squamous epithelium.
40What type of epithelium forms the mesothelial lining of serous cavities?
Simple squamous epithelium.
41What is the microscopic appearance of simple cuboidal epithelium?
Regular rows of cylindrical cells that appear approximately square in vertical section and polygonal in horizontal section.
42What is the shape of the nucleus in simple cuboidal epithelium?
Centrally placed and round.
43List the examples of simple cuboidal epithelium given in the lecture.
Germinal epithelium of the ovary; lining of thyroid follicles; choroid plexus; inner surface of the lens capsule; pigment layer of the retina; excretory ducts and secretory alveoli of many glands.
44What type of epithelium lines thyroid follicles?
Simple cuboidal epithelium.
45What type of epithelium forms the pigment layer of the retina?
Simple cuboidal epithelium.
46What is the microscopic appearance of simple columnar epithelium?
Regular rows of cylindrical cells that are taller than their diameter in vertical section and polygonal in horizontal section.
47Where is the nucleus located in simple columnar epithelium?
Basally, and it is elongated and oval.
48What surface modification may be present on simple columnar epithelium?
A striated border or microvilli projecting from the apical surface.
49List the non-ciliated examples of simple columnar epithelium given in the lecture.
Lining of the alimentary canal from stomach to rectum, gall bladder, and endometrium of the uterus.
50List the ciliated examples of simple columnar epithelium given in the lecture.
Ependyma of the spinal cord, ventricles of the brain, part of uterine tubes, small bronchi, and bronchioles.
51What are the main features of stratified squamous non-keratinized epithelium?
It is thick and has several layers; only the deepest layer contacts the basement membrane; basal cells are cuboidal, middle cells are polyhedral, and surface cells are flattened.
52Why is stratified squamous non-keratinized epithelium described as non-keratinized?
The surface cells retain an oval nucleus.
53List the examples of stratified squamous non-keratinized epithelium.
Lining of the mouth, pharynx, oesophagus, vagina, cornea, and anal canal.
54How does stratified squamous keratinized epithelium differ from non-keratinized epithelium according to the lecture?
Its superficial layer is composed of dead cells whose nuclei and cytoplasm have been replaced with keratin substances.
55What is the main example of stratified squamous keratinized epithelium?
The epidermis covering the whole surface of the body.
56How many layers of cuboidal cells are present in stratified cuboidal epithelium?
Two layers.
57Which layer of stratified cuboidal epithelium rests on the basement membrane?
The basal layer.
58Where is stratified cuboidal epithelium found?
In the main ducts of glands and ducts of sweat glands.
59What are the layers of stratified columnar epithelium?
The deeper layer consists of low columnar to cuboidal cells, middle layers contain polyhedral cells, and the superficial layer contains columnar cells.
60Which part of stratified columnar epithelium contacts the basement membrane?
The deeper layer.
61Where is stratified columnar epithelium found?
Conjunctiva of the eye, certain large excretory ducts, and the penile part of the male urethra.
62Why does pseudostratified columnar epithelium appear stratified?
Its cells have different heights and their nuclei are located at different levels.
63Do all cells of pseudostratified columnar epithelium contact the basement membrane?
Yes, all cells contact the basement membrane.
64Do all cells of pseudostratified columnar epithelium reach the surface?
No, only some cells reach the surface.
65What is the shape of pseudostratified cells that do not extend to the surface?
They usually have a broad base and become narrow at their apical end.
66What is the shape of pseudostratified cells that reach the surface?
They have a narrow base contacting the basement membrane and a broadened apical surface.
67List the examples of pseudostratified columnar epithelium given in the lecture.
Nasal cavity, trachea, large bronchi, epididymis, and vas deferens.
68What is transitional epithelium also called?
Urothelium.
69Where is transitional epithelium found?
The lower urinary tract.
70What special property does urothelium have?
Its morphology allows it to distend.
71What is the permeability property of urothelium?
It is essentially impermeable to salts and water.
72How does the number of cell layers of urothelium vary in the urinary tract?
It begins in the minor calyces as two layers, increases to four to five layers in the ureter, and reaches six or more layers in an empty bladder.
73How does urothelium change when the bladder is distended?
Up to three layers are seen.
74Why does urothelium change its appearance when the bladder is distended?
The cells accommodate the increasing surface area by flattening and unfolding.
75What happens to the large surface cells of urothelium during bladder distension?
They become flattened and unfold to accommodate the increasing surface area.
76Why can urothelium appear to have three true layers when the bladder is distended?
Individual cells unfold and flatten, giving the appearance of three layers of stratification.
77How does urothelium usually appear in routine histological sections?
Because sections are usually obtained from the empty bladder, surface epithelial cells are usually cuboidal and bulge into the luminal surface.
78Why are the surface cells of urothelium called dome or umbrella cells?
Because of the curvature of their apical surface.
79List the examples of transitional epithelium.
Pelvis of the kidney, ureters, urinary bladder, and proximal part of the urethra.
80What are the surface modifications of epithelium listed in the lecture?
Cilia, stereocilia, microvilli, and glycocalyx.
81What is a cilium?
A long hair-like projection of the plasma membrane.
82What is the function of ciliary beating?
Cilia beat in one direction to move entangled particles from the surface.
83In which direction do respiratory cilia beat?
Towards the pharynx.
84In which direction do cilia of the uterine tube beat?
Towards the uterus.
85What is a microvillus?
A minute finger-like projection of the plasma membrane.
86What is the main function of microvilli?
To increase surface area for better absorption.
87How do microvilli transport absorbed material according to the lecture?
By microfilaments in their central core.
88What other function do microvilli participate in?
Carbohydrate digestion.
89Are the microvilli described in the lecture as motile?
No, they are non-motile.
90Where are microvilli seen according to the lecture?
In the intestine.
91What is a stereocilium?
A very long, thick microvillus that is non-motile and may branch.
92What is one function of stereocilia?
Increasing surface area for better absorption.
93Where are stereocilia found for absorption?
In the epididymis.
94Where are stereocilia involved in perception of stimuli?
In the inner ear.
95What is the glycocalyx?
A surface coat over the absorptive epithelium of the small intestine.
96What is the glycocalyx rich in?
Polysaccharides.
97What else does the glycocalyx contain?
Proteins and hydrolytic enzymes.
98What does the glycocalyx do to ions before intestinal absorption?
It concentrates the ions before their absorption.
99What receptor-related function does the glycocalyx have?
It acts as a receptor site for hormones and enzymes.
100What is the relationship between epithelial structure and function?
The distinctive microscopic structure and arrangement of cells help indicate what the cell or tissue is designed to do.
101How can microscopic anatomy help differentiate organs?
The type, location, and function of epithelium can help differentiate organs such as the GIT, urinary tract, ureter, and appendix.
102What epithelial type is associated with the GIT in the examples given in the lecture?
Simple columnar epithelium.
103What epithelial type is associated with the urinary tract in the examples given in the lecture?
Transitional epithelium.
104What is epithelial metaplasia listed under the applied aspects of the lecture?
Epithelial metaplasia.
105What clinical condition is also known as immotile cilia syndrome?
Primary ciliary dyskinesia (PCD).
106What structures are identified as targets of pathogenic agents under the applied aspects?
Junctional complexes.
107What malignant condition is listed under the applied aspects of epithelium?
Malignant tumours of glands.