Lecture 1 - Histology

Question 1

Functions of Epithelia

Answer 1

Protection- skin 
Absorption- intestines 
Transport material at surface- mediated by cilia 
Secretion -glands 
Excretion- tubules of kidneys 
Gas exchange - lung alveolus 
Gliding between surfaces - mesothelium

Question 2

Epithelia Characteristics

Answer 2

• Derived from all 3 germ layers: ectoderm, mesoderm, endoderm
• Exist all over body except: articular cartilage, tooth enamel, anterior surface of iris
• Most renew continuously by mitosis
• Are avascular, nutrients from connective tissue via diffusion
• Highly cellular (little or no matrix)
• Have basal membrane

Question 3

Simple Squamous

Answer 3

-Tight sheet of cells connected by tight junctions
-Nucleus is flat/oval, in center, little cytoplasm
-Located in -blood vessels (endothelium) -body cavities (mesothelium) -Bowman’s capsule of kidneys -Alveoli
Functions: -Fluid transport -Gas exchange -Lubrication

Question 4

Simple Cuboidal

Answer 4

-Have central, round nucleus
-Located in -Small ducts of exocrine glands -Most of kidney tubules -Thyroid follicles
Functions: -Protection -Absorption- Secretion -Conduit

Question 5

Simple Columnar

Answer 5

-Each cell rests on basement membrane, ovoid nucleus located basally
-Have specialized apical projections (microvilli/cilia)
-Located in lining of stomach/intestines/gallbladder
/uterus/oviducts
-Functions: -Protection -Absorption- Secretion -Transport

Question 6

Stratified Squamous

Answer 6

Nonkeratinized: -Found in lining moist cavities (oral cavity, vagina) -Have nucleus -Function is protective barrier
Keratinized: -Found in epidermis of thick skin and consists of surface layers of dead cells filled w keratin and no nucleus

Question 7

Stratified Cuboidal

Answer 7

-Found lining sweat glands

Question 8

Stratified Columnar

Answer 8

-Found in conjunctiva of eye and ducts of some large glands

Question 9

Pseudostratified

Answer 9

• Appears stratified, but is single layer w all cells attached to basal layer. Some cells are wider and do not reach apical surface
• Nucleus is basal in fatter cells and higher in thinner cells, so it appears stratified
• Ciliated: found in many portions of respiratory tract
• Nonciliated: found in ducts of male urethra and epididymis
• Functions: -protection -motility -sensory perception

Question 10

Transitional

Answer 10

• 2-6 layers of cells found exclusively in urinary bladder, ureters, parts of urethra
• Distensible property
• Lower cells are cuboidal, apical layers very in shape. When bladder is full, apical cells are flatter, when empty they have rounded dome appearance. Apical cells have intracellular plaques for physical shield
• Function: -protection

Question 11

Epithelial Glands

Answer 11

• Most glands develop as epithelial outgrowths into underlying connective tissue
  1. Exocrine: Remain connected to surface by excretory duct that transports secretory product to outside
  2. Endocrine: Lack an excretory duct, product is released into blood circulation

Question 12

Celiac Diseae

Answer 12

• Gluten sensitivity enteropathy

- disorder of small intestines, loss of microvilli brush border of absorptive cells

Question 13

Primary Ciliary Diskinesia

Answer 13

• immotile cilia syndrome

- Kartagener’s syndrome: chronic respiratory infections (lack of cleansing cilia), infertility (immotile spermatazoa)

Question 14

Epithelial Metaplasia

Answer 14

• eversible conversion to one type of epithelial cells into another
• Adaptive response to stress/chronic inflammation
• In smokers, ciliated pseudostratified columnar epithelium of bronchi -> stratified simple squamous