General Histology

Question 1

What are the four different tissue types?

Answer 1

Connective tissue
Muscle tissue
Nerve tissue
Epithelial tissue

Question 2

What are the three subtypes of connective tissue?

Answer 2

Adipose tissue
Cartilage
Bone tissue

Question 3

What are the five types of neurons and where are the main places they are found?

Answer 3

Bipolar neurons- Retina
Unipolar/Pseudopolar neurons- Spine and ganglia
Multipolar neurons- Motor cells
Pyramidal cells- Hippocampus
Purkinje cells- Cerebellum

Question 4

What are the 5 types of nervous tissue?

Answer 4

Neurons
Neuroglia
Melanocytes
Odontoblasts
Chromaffin

Question 5

What is the role of glial cells and what are the subtypes?

Answer 5

Glial cells serve a homeostatic role (structural and nutritional support, insulation of neurons, phagocytosis of pathogens)

Subtypes include
Astrocytes
Oligodendrocytes
Schwann cells
Microglia
Ependymal cells

Question 6

What are astrocytes?

Answer 6

Astrocytes are star-shaped glial cells of the central nervous system that support the epithelial cells of the blood-brain barrier, maintain extracellular osmotic homeostasis, and moderate the healing and scarring process.

Question 7

What are oligodendrocytes?

Answer 7

Oligodendrocytes are glial cells of the central nervous system that myelinates nerves.

Question 8

What are schwann cells?

Answer 8

Schwann cells are glial cell that myelinates the axons of motor and sensory peripheral neurons. Disorders of these cells include neoplasms (e.g., schwannoma, acoustic neuroma) and demyelinating disorders (e.g., Charcot–Marie–Tooth disease, Guillain–Barré syndrome).

Question 9

What are microglia?

Answer 9

Microglia are e macrophages of the central nervous system, which activate in response to tissue damage. Derived from mesoderm.

Question 10

What are ependymal cells?

Answer 10

Ependymal cells are a specialized type of epithelial cells that line the ventricular system of the brain and play a key role in the production of cerebrospinal fluid.

Question 11

What are melanocytes and where are they found?

Answer 11

Melanocytes are the pigment-containing cells of the skin that produce melanin. Melanin production is stimulated by melanocyte stimulating hormone and ultraviolet radiation. Malignant transformation of melanocytes causes melanoma. Also found in retina.

Question 12

What are odontoblasts and where are they found?

Answer 12

Odontoblasts are cells involved in the formation of dentin in teeth. Originate from neural crest cells.

Question 13

What are chromaffin cells and where are they found?

Answer 13

Chromaffin cells are a group of neuroendocrine cells found in the adrenal medulla and other ganglia of the sympathetic nervous system. Release epinephrine and norepinephrine.

Question 14

What are the types of muscle tissue?

Answer 14

Striated (includes cardiac and skeletal)

Smooth muscle

Question 15

What are the two functional types of epithelium?

Answer 15

Surface and glandular epithelium

Question 16

Epithelial tissue covers all inner and outer surfaces of the body EXCEPT what?

Answer 16

The synovial membrane is composed of synoviocytes (not epithelial cells!), which line the inner surfaces of joint capsules, synovial bursa, and tendon sheaths.

Question 17

What types of epithelia are formed from the three germ layers?

Answer 17

Ectoderm- Epithelium of skin and skin appendages.
Mesoderm- Epithelium of serous membranes (mesothelium) which is found in peritoneum, pleural, and pericardial cavities. ALSO Cells lining the inner surface of blood and lymphatic vessels (endothelium).
Endoderm: epithelium of the respiratory and gastrointestinal tract.

Question 18

What are the differences between simple, pseudostratified, and stratified epithelium?

Answer 18

Simple epithelium: a single layer of epithelial cells with all cells attached to the basement membrane
Pseudostratified epithelium: a single layer of cells with the appearance of multiple layers as a result of the nuclei positioned at different levels
Stratified epithelium: two or more cell layers with the basal layer attached to the basement membrane

Question 19

What are differences between squamous, cuboidal, and columnar epithelium?

Answer 19

Flat (squamous epithelium)
Appearance: Upper cells have a squamous (flat) shape (width > height).
Examples: skin , esophagus , cervix , serous membrane (e.g., peritoneum)
Cube-shaped (cuboidal epithelium)
Appearance: Upper cells have a cube-like shape (width = height).
Examples: bile ducts , renal tubules
Column-shaped (columnar epithelium)
Appearance: Upper cells have a rectangular or cylindrical shape (width < height).
Examples: intestine , respiratory tract (respiratory epithelium)

Question 20

Microvilli and stereocilia are composed of (?) while kinocilia are composed of (?)

Answer 20

Microvilli and stereocilia are composed of ACTIN FILAMENTS while kinocilia are composed of MICROTUBULES

Question 21

What are the two intraepithelial gland types?

Answer 21

1. Goblet cells
   Definition: single intraepithelial glandular cells with a vacuole that is characteristically filled with mucus (goblet form)
   Function: secrete mucus (mucins)
   Distribution
   Small and large intestines
   Nasal mucosa and respiratory tract
2. Secretory epithelium
   Definition: conglomerates of columnar epithelial cells with a bright cytoplasm (filled with mucus) and no vacuole
   Distribution: e.g., the surface epithelium of the stomach and cervical canal is entirely composed of secretory epithelium

Question 22

What are the two components of a typical extrathelial gland?

Answer 22

1. Terminal ends
   Definition: A closed glandular section that is connected to the excretory ducts and is the site of secretion production. There are numerous types of terminal ends.
   Function: production and release of secretions into the lumen (the secretion drains from here into the excretory duct system)
2. Definition: ducts lined with epithelial cells that connect glandular cells (in the acinus) with the opening of the gland
   Function: drainage of secretion; changes in the nature of the secretion (e.g., through the addition/removal of ions)
   Shapes: Because extraepithelial glands are usually subdivided into lobules (or lobuli) by connective tissue septa, there are various forms of excretory ducts.

Question 23

What are the four shapes of exocrine gland terminal ends?

Answer 23

1. Acinar glands
   Form: berry-like , narrow lumen
   Examples: parotid gland, pancreas
2. Alveolar glands
   Shape: sac-like , wide lumen
   Examples: apocrine sweat glands
3. Tubular glands
   Shape: tubular; wide, elongated lumen
   Examples: gastric glands (foveolas in the stomach), colonic crypts
   Subtypes
   Simple branched tubular (e.g., meibomian glands)
   Coiled tubular (e.g., eccrine sweat glands)
4. Mixed forms: tubuloacinar, tubuloalveolar

Question 24

What are the 4 secretory mechanisms of exocrine glands?

Answer 24

1. Eccrine secretion
   Definition: release of ions and small molecules through transmembrane proteins
   Mechanism: membrane protein transport
   Distribution: in almost all exocrine gland cells
2. Merocrine secretion
   Definition: release of secretions rich in proteins through fusion of cytosolic vesicles with the cell membrane
   Mechanism: exocytosis
   Distribution: in almost all exocrine glandular cells
3. Apocrine secretion
   Definition: release of secretions rich in lipids via budding off of a part of the apical cytoplasm
   Mechanism: A portion of the cell membrane buds off with cytoplasm containing the secretory product (e.g., milk lipid droplets). As a result, the gland cell becomes smaller.
   Distribution: found only in apocrine sweat glands and lactating mammary glands
4. Holocrine secretion
   Definition: release of the entire cytoplasmic content through destruction of the gland cell
   Mechanism: apoptosis of the glandular cell
   Distribution: found only in sebaceous glands

Question 25

What are the 3 categories of secretion glands?

Answer 25

1. Serous glands
   Secretion: low viscosity and rich in proteins and enzymes
   Histological characteristics
   Terminal end: mainly acinar (→ acinar glands)
   Gland cells: basal part is rich in rough endoplasmic reticulum (basophilic staining), apical granular secretions (eosinophilic staining)
   Examples: parotid gland, pancreas
2. Mucous glands
   Secretion: viscous and rich in mucin
   Histological characteristics
   Terminal end: mainly tubular (→ tubular glands)
   Gland cells: pale, bright cytoplasm
   Examples: sublingual gland, esophageal glands, Brunner’s glands, all intraepithelial glands
3. Seromucous glands
   Secretion: mainly low viscosity and contains both mucin and enzymes
   Histological characteristics
   Terminal end: mainly tubuloacinar; often show a serous demilune
   Gland cells: characteristics of serous and also mucous cells
   Examples: submandibular gland.

Question 26

What are myoepithelial cells?

Answer 26

Definition: specialized epithelial cells that contain actin and myosin filaments, and contract when stimulated
Function: contraction (through proteins of the smooth muscles such as actin, myosin, and desmin filaments) → expulsion of the gland secretion
Appearance: star-shaped, branching
Distribution: between glandular epithelium in several glands
Sweat, salivary, and lacrimal glands
Mammary glands
Esophageal glands
Respiratory tract

Question 27

What is the basement membrane and its structure?

Answer 27

Definition: a band-like structure consisting of components of the extracellular matrix that is found between epithelial cells and connective tissue
Function
Anchoring epithelium to connective tissue
Diffusion barrier
Distribution: The basement membrane connects connective tissue with the following cell types:
Epithelium and endothelium
Glial cells
Adipocytes and myocytes
Structure: The basement membrane consists of the basal lamina (contains two layers) and the lamina fibroreticularis.
Basal lamina (adjacent to the epithelium)
Lamina lucida (lamina rara)
Integrins
Collagen type XVII (BP 180, or bullous pemphigoid protein 180)
Lamina densa
Collagen type IV
Laminin
Lamina reticularis (adjacent to the connective tissue)
Reticular fibers
Anchorage with the basement membrane through collagen type III fibrils