Dentosphere : World of Dentistry

Acellular, condensed layer that forms a barrier

# An acellular, condensed layer that forms a barrier between the epithelium and connective tissues is called:

A. Basement membrane

B. Gap junctions

C. Desmosomes

D. Luminal surface

The correct answer is A. Basement membrane.

An acellular, condensed layer that forms a barrier between the epithelium and connective tissues is called basement membrane (lamina). Luminal surface is the surface of the lumen and may contain specialized structures such as cilia, microvilli, or sterocilia. Desmosomes (macula densa) are small, circular patches deep in the zonula adherens. Gap junctions are small pores found between adjacent cells that allow the passage of small molecules.

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Which of the following is not an important division of subclavian artery?

# Which of the following is not an important division of subclavian artery?

A. Thyrocervical trunk

B. Internal thoracic artery

C. Carotid artery

D. Vertebral artery

The correct answer is C. Carotid artery.

A. VERTEBRAL ARTERY: Supplies the brain.

B. INTERNAL THORACIC ARTERY: Descends to supply the diaphragm and terminates as the superior epigastric artery, which helps to supply the abdominal wall.

C. THYROCERVICAL OR CERVICOTHYROID TRUNK: Divides into three arteries- the transverse cervical artery, suprascapular artery and the inferior thyroid artery.

D. COSTOCERVICAL TRUNK: divides into two branches- the superior intercostals and deep cervical arteries, which supply muscles of intercostal spaces.

E. DORSAL SCAPULAR ARTERY: supplies the muscles of the scapular region.

Carotid artery is not a part of subclavian artery.

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The most abundant protein in humans is:

# The most abundant protein in humans is:

A. Fatty acids

B. Fiber

C. Carbohydrates

D. Collagen

The correct answer is D. Collagen.

Collagen is the most abundant protein in human body, characterized by its high rigidity and tensile strength.

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Which of the following collagen is found in cartilage?

# Which of the following collagen is found in cartilage?

A. Type 1

B. Type 2

C. Type 3

D. Type 4

The correct answer is B. Type 2.

Several types of Collagen are found in different body tissues.

a. Type I - Skin, tendon, bone, dentin

b. Type II - Cartilage

c. Type III - Aorta, fetal skin

d. Type IV - Basement membrane

e. Type V - Placenta, Skin

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Percentage of proline in collagen

# Approximately one third of collagen is glycine and about _______ is proline.

A. 14 %

B. 12 %

C. 10 %

D. 5 %

The correct answer is C. 10 %.

Approximately one third of collagen is glycine (every third position) and ten percent is proline.

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Fibrous, insoluble protein derived from epidermis is:

# ________ is fibrous, insoluble protein derived from epidermis.

A. Collagen

B. Keratin

C. Elastin

D. Myofibril

The correct answer is B. Keratin.

Keratin is fibrous and insoluble protein derived from epidermnis. Elastin is rich in proline and other non polar side chains. Approximately one third of elastin is composed of amino acid glycine.

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