Chapter 5 - Epithelia and Glands

Question 1

Which one of the following statements about the desmosome is true?
(A) It is sometimes called a nexus.
(B) It permits the passage of large proteins
from one cell to an adjacent cell.
(C) It has a plaque made up of many connexons.
(D) It facilitates metabolic coupling between adjacent cells.
(E) It is a disk-shaped adhesion site between epithelial cells.

Answer 1

E. Desmosomes are sites of adhesion characterized by dense cytoplasmic plaques and associ­ated keratin filaments. Only gap junctions permit cell-to-cell communication of small mol ecules via their connexon channels (see Chapter 5 II A) .

Question 2

A medical student who has chronic lower respiratory infections seeks the advice of an ear, nose, and throat specialist. A biopsy of the stu­dent's respiratory epithelium reveals alterations in certain epithelial structures. This patient is most likely to have abnormal
(A) microvilli
(B) desmosomes
(C) cilia
(D) hemidesmosomes
(E) basal plasmalemma infoldings

Answer 2

C. Individuals with abnormal respiratory cilia commonly have recurrent respiratory infections if the cilia are unable to clear the respiratory epithelium of microorganisms, debris, and so forth. The student may have immotile cilia syndrome, which is caused by a genetic defect, resulting in cilia with axonemes that lack ciliary dynein arms and thus are unable to beat (see Chapter 5 IV C 2 Clinical Considerations).

Question 3

Which one of the following statements about the gap junction is true?
(A) It extends as a zone around the apical perimeter of adjacent cells.
(B) It possesses dense plaques composed in part of desmoplakins.
(C) It permits the passage of ions from one cell to an adjacent cell.
(D) Its adhesion is dependent upon calcium ions.
(E) It possesses transmembrane linker glycoproteins.

Answer 3

C. The gap junction channel regulates the passage of ions and small molecules from cell to cell, excluding those having a molecular weight greater than 1200 Da. The tight junction is the zone of adhesion around the apical perimeter of adjacent cells. The other statements are characteris­tics of desmosomes (see Chapter 5 II B).

Question 4

Which one of the following statements about glands is true?
(A) Exocrine glands lack ducts.
(B) Simple glands have ducts that branch.
(C) Endocrine glands secrete into ducts.
(D) Serous secretions are watery.
(E) Holocrine glands release their contents by exocytosis

Answer 4

D. Serous secretions produced by glands are often rich in enzymes and watery in consistency. Exocrine glands secrete into ducts, and endocrine glands lack ducts. Merocrine glands use exo­cytosis to release their products (see Chapter 5 V B).

Question 5

Which one of the following statements about epithelia is true?
(A) They are polarized.
(B) They are vascular.
(C) They are completely surrounded by a basal lamina.
(D) They contain wide intercellular spaces.
(E) They are not part of the wall of blood vessels

Answer 5

A. Epithelia are polarized, meaning they show sidedness and have apical and basolateral sur­faces with specific functions (see Chapter 5 I A).

Question 6

Which one of the following statements about cilia is true?
(A) They possess a 9 + 0 configuration of microtubules.
(B) They do not contain an axoneme.
(C) They contain ciliary dynein arms.
(D) They are nearly identical to centrioles.
(E) They play a major function in absorption.

Answer 6

C. Cilia contain an axoneme with ciliary dynein arms extending unidirectionally from one member of each doublet. Ciliary dynein has ATPase activity, and when it splits ATP, the adjacent doublets slide past one another and the cilium moves. Microvilli, not cilia, function in absorp­tion (see Chapter 5 IV C).

Question 7

Which one of the following statements about stratified squamous epithelium is true?
(A) The surface layer of cells is always keratinized.
(B) The cells in its most superficial layer are flattened.
(C) Its basal cells rest on an elastic lamina. (D) Its cells lack desmosomes.
(E) It lines the ducts of sweat glands.

Answer 7

B. Stratified squamous epithelium is characterized by flattened cells with or without nuclei in its superficial layer. It may or may not be keratinized, and it rests on a basal lamina produced by the epithelium. Stratified cuboidal epithelium lines the ducts in sweat glands (see Chapter 5 I B).

Question 8

Which one of the following is an autoimmune disease?
(A) Adenocarcinoma
(B) Bullous pemphigoid
(C) Carcinoma
(D) First-degree burn
(E) Immotile cilia syndrome

Answer 8

B. Bullous pemphigoid is an autoimmune disease. Affected individuals form antibodies against their own hemidesmosomes (see Chapter 5 III B Clinical Considerations).

Question 9

Which one of the following is a hereditary disease that may be associated with infertility?
(A) Adenocarcinoma
(B) Bullous pemphigoid (C) Carcinoma
(D) Edema
(E) Immotile cilia syndrome

Answer 9

E. Immotile cilia syndrome results from a genetic defect that prevents synthesis of ciliary dynein ATPase, resulting in cilia that cannot actively move. Men are sterile because their sperm are not motile (the flagella in their tails lack this enzyme). Women may be infertile because cilia along their oviducts may fail to move oocytes toward the uterus (see Chapter 5 IV C 2 Clinical Considerations) .

Question 10

Which one of the following is a tumor arising from glandular epithelium?
(A) Adenocarcinoma
(B) Bullous pemphigoid
(C) Carcinoma
(D) Edema
(E) Immotile cilia syndrome

Answer 10

A. Adenocarcinomas are epithelial tumors that originate in glandular epithelia. Carcinomas originate from surface epithelia (see Chapter 5 V B 2 Clinical Considerations).

Question 11

Which of the following is a condition affect­ing the epidermis of the skin in which blisters do not form?
(A) Adenocarcinoma
(B) Bullous pemphigoid
(C) Carcinoma
(D) First-degree burn
(E) Immotile cilia syndrome

Answer 11

D. First-degree burns damage the upper layers of the epidermis only, and blisters do not form in the skin (see Chapter 5 I C Clinical Considerations).