2.3

Question 1

Basal Epithelial Surfaces

Answer 1

• Basal Lamina
• Hemidesmosomes
• Basal plasma membrane infoldings

Question 2

• Basal Lamina
• Hemidesmosomes
• Basal plasma membrane infoldings

Answer 2

Basal Epithelial Surfaces

Question 3

The _____________ is an extracellular supportive structure 20 to 100 nm thick that is visible only by electron microscopy. It is produced by the epithelium resting upon it and is composed mainly of type IV collagen, laminin, entactin, and proteoglycans (rich in heparan sulfate).

Answer 3

Basal lamina

Question 4

The basal lamina is an extracellular supportive structure 20 to 100 nm thick that is visible only by electron microscopy. It is produced by the epithelium resting upon it and is composed mainly of ____________, __________, _______________, and __________ (rich in heparan sulfate).

Answer 4

Type IV collagen, laminin, entactin, and proteoglycans

Question 5

Basal Lamina

Answer 5

1. It consists of two zones: the lamina lucida (or lamina rara), which lies next to the plasma membrane, and the lamina densa, a denser meshwork of type IV collagen, glycoproteins, and glycosaminoglycans, which lies adjacent to the reticular lamina of the deeper connective tissue.
2. The basal lamina plus the underlying reticular lamina constitute the basement membrane, which is observable by light microscopy.

Question 6

Basal Lamina:

It consists of two zones: the ___________ (or lamina rara), which lies next to the plasma membrane, and the ___________, a denser meshwork of type IV collagen, glycoproteins, and glycosaminoglycans, which lies adjacent to the reticular lamina of the deeper connective tissue.

Answer 6

Lamina lucida; lamina densa

Question 7

Basal Lamina:

The basal lamina plus the underlying __________constitute the basement membrane, which is observable by light microscopy

Answer 7

Reticular lamina

Question 8

____________are specialized junctions that resemble half of a desmosome. They mediate adhesion of epithelial cells to the underlying extracellular matrix.

Answer 8

Hemidesmosomes

Question 9

Hemidesmosomes:

Answer 9

1. These junctions are present on the basal surface of basal cells in certain epithelia (e.g., tracheal epithelium and stratified squamous epithelium) and on myoepithelial cells, where they lie adjacent to the basal lamina.
2. They consist of a dense cytoplasmic plaque, which is linked via transmembrane receptor proteins (integrins) to laminins in the basal lamina. Anchoring filaments (type VII collagen) from the basal lamina extend deeper into the underlying connective tissue and insert into plaques of type IV collagen.
3. Keratin filaments (tonofilaments) in the cell terminate in the hemidesmosome plaque, allowing these junctions to link the cytoskeleton with the extracellular matrix.

Question 10

Hemidesmosomes:

These junctions are present on the basal surface of _______ cells in certain epithelia (e.g., tracheal epithelium and stratified squamous epithelium) and on __________cells, where they lie adjacent to the basal lamina

Answer 10

Basal; Myoepithelial

Question 11

Hemidesmosomes:

They consist of a _________________, which is linked via transmembrane receptor proteins (integrins) to laminins in the basal lamina. Anchoring filaments (type VII collagen) from the basal lamina extend deeper into the underlying connective tissue and insert into plaques of type IV collagen

Answer 11

Dense cytoplasmic plaque;

Question 12

Hemidesmosomes:

________ filaments (tonofilaments) in the cell terminate in the hemidesmosome plaque, allowing these junctions to link the cytoskeleton with the extracellular matrix.

Answer 12

Keratin

Question 13

____________________ are common in ion-transporting epithelia (e.g., distal convoluted tubule of the kidney, striated ducts in salivary glands).

Answer 13

Basal plasma membrane infoldings

Question 14

Basal plasma membrane infoldings are common in ______________________ (e.g., distal convoluted tubule of the kidney, striated ducts in salivary glands).

Answer 14

Ion-transporting epithelia

Question 15

Basal plasma membrane infoldings

Answer 15

1. They form deep invaginations that compartmentalize mitochondria.
2. Function. They increase the surface area and bring ion pumps (Na_–K_ adenosine triphosphatase [ATPase]) in the plasma membrane close to their energy supply (ATP produced in mitochondria).

Question 16

Basal plasma membrane infoldings:

They form deep invaginations that compartmentalize ______________

Answer 16

Mitochondria

Question 17

Basal plasma membrane infoldings:

Function. They increase the _____ and bring ion pumps (Na_–K_ adenosine triphosphatase [ATPase]) in the plasma membrane close to their ____________ (ATP
produced in mitochondria).

Answer 17

Surface area; Energy supply