21.3 Primary Lymphoid Structures

At what age does the thymus reach its maximum weight?

Puberty

What happens to the cells within the thymus after it reaches its maximum size?

They begin to regress

What replaces much of the thymic tissue after it regresses?

Adipose connective tissue

Apart from lymphoid cells, what other type of tissue is found in the thymus?

Epithelial tissue Signup and view all the answers

Which hormone is NOT produced and secreted by the thymus?

Insulin Signup and view all the answers

In a child, how many thymic lobes are present and how are they surrounded?

Two lobes, each surrounded by a connective tissue capsule Signup and view all the answers

Where is red bone marrow located in adults?

Within trabeculae in portions of spongy bone within the skeleton Signup and view all the answers

What is the primary function of red bone marrow?

Hematopoiesis (production of formed elements) Signup and view all the answers

Which of the following is NOT considered a formed element produced in red bone marrow?

Plasma cells Signup and view all the answers

Where must T-lymphocytes migrate to complete their maturation?

Thymus Signup and view all the answers

What are the two major types of lymphocytes mentioned in the text?

B-lymphocytes and T-lymphocytes Signup and view all the answers

What type of cells must migrate to the thymus after being formed in red bone marrow?

T-lymphocytes Signup and view all the answers

Why are T-lymphocytes named as such?

Because they complete their maturation in the thymus. Signup and view all the answers

Why do B-lymphocytes have the 'B' in their name?

From their maturation in the bursa of fabricius. Signup and view all the answers

What is the primary function of the thymus?

Maturation of T-lymphocytes Signup and view all the answers

Where do immature T-lymphocytes migrate to complete their maturation?

Thymus Signup and view all the answers

Why do humans lack the bursa of fabricius?

Because B-lymphocytes mature in the bone marrow Signup and view all the answers

What is the function of red bone marrow?

Development of formed elements through hematopoiesis Signup and view all the answers

Where are trabeculae found in the thymic lobes?

Subdividing the lobes into lobules Signup and view all the answers

What is the primary composition of both the outer cortex and inner medulla of a thymic lobule?

Epithelial tissue infiltrated with T-lymphocytes Signup and view all the answers

What is the main function of the epithelial cells in the thymus?

To secrete thymic hormones that aid in T-lymphocyte maturation Signup and view all the answers

Why is the thymus described as a lymphoepithelial organ?

Because it contains both lymphoid cells and epithelial tissue Signup and view all the answers

Where do mature T-lymphocytes reside within a thymic lobule?

In the inner medulla Signup and view all the answers

What is the approximate maximum weight of the thymus in children?

30 to 50 grams Signup and view all the answers

What type of tissue replaces much of the thymic tissue after it regresses?

Connective tissue Signup and view all the answers

What is the primary function of the epithelial tissue found in the thymus?

To produce and secrete hormones Signup and view all the answers

How many thymic lobes are present in a child's thymus?

2 Signup and view all the answers

What is the main function of the thymus?

To house and mature T-lymphocytes Signup and view all the answers

What is the composition of the outer cortex and inner medulla of a thymic lobule?

Both lymphoid cells and epithelial cells Signup and view all the answers

Which of the following is NOT a location for red bone marrow in adults?

Phalanges Signup and view all the answers

What is the unique step required by T-lymphocytes in their maturation?

They must migrate to the thymus Signup and view all the answers

Which of the following is NOT considered a formed element produced in red bone marrow?

Fibroblasts Signup and view all the answers

What is the process of production of formed elements called?

Hematopoiesis Signup and view all the answers

Which of the following is NOT a major type of lymphocyte mentioned in the text?

Natural killer cells Signup and view all the answers

After being produced in the red bone marrow, where do most formed elements move directly?

The blood Signup and view all the answers

What is the reason for the name 'T-lymphocytes'?

They require the thymus gland for maturation. Signup and view all the answers

Why were B-lymphocytes given their name?

They mature in the bursa of fabricius in birds. Signup and view all the answers

What is the primary function of the thymus?

Maturation of T-lymphocytes Signup and view all the answers

Where do immature T-lymphocytes originate from before migrating to the thymus?

Bone marrow Signup and view all the answers

What is the primary function of red bone marrow?

Production of formed elements through hematopoiesis Signup and view all the answers

What cells are primarily responsible for the maturation of T-lymphocytes within the thymus?

Epithelial cells Signup and view all the answers

What structures subdivide the thymic lobes into lobules?

Trabecular extensions called trabeculae or septa Signup and view all the answers

Which part of a thymic lobule contains immature T-lymphocytes?

Cortex Signup and view all the answers

What type of cells secrete thymic hormones that participate in T-lymphocyte maturation?

Epithelial cells Signup and view all the answers

What term is used to describe the thymus due to its composition of lymphoid cells and epithelial tissue?

Lymphoepithelial organ Signup and view all the answers

Where are the details of T-lymphocyte maturation described?

In section 22.5 Signup and view all the answers

21.3 Primary Lymphoid Structures

Questions and Answers

At what age does the thymus reach its maximum weight?

What happens to the cells within the thymus after it reaches its maximum size?

What replaces much of the thymic tissue after it regresses?

Apart from lymphoid cells, what other type of tissue is found in the thymus?

Which hormone is NOT produced and secreted by the thymus?

In a child, how many thymic lobes are present and how are they surrounded?

Where is red bone marrow located in adults?

What is the primary function of red bone marrow?

Which of the following is NOT considered a formed element produced in red bone marrow?

Where must T-lymphocytes migrate to complete their maturation?

What are the two major types of lymphocytes mentioned in the text?

What type of cells must migrate to the thymus after being formed in red bone marrow?

Why are T-lymphocytes named as such?

Why do B-lymphocytes have the 'B' in their name?

What is the primary function of the thymus?

Where do immature T-lymphocytes migrate to complete their maturation?

Why do humans lack the bursa of fabricius?

What is the function of red bone marrow?

Where are trabeculae found in the thymic lobes?

What is the primary composition of both the outer cortex and inner medulla of a thymic lobule?

What is the main function of the epithelial cells in the thymus?

Why is the thymus described as a lymphoepithelial organ?

Where do mature T-lymphocytes reside within a thymic lobule?

What is the approximate maximum weight of the thymus in children?

What type of tissue replaces much of the thymic tissue after it regresses?

What is the primary function of the epithelial tissue found in the thymus?

How many thymic lobes are present in a child's thymus?

What is the main function of the thymus?

What is the composition of the outer cortex and inner medulla of a thymic lobule?

Which of the following is NOT a location for red bone marrow in adults?

What is the unique step required by T-lymphocytes in their maturation?

Which of the following is NOT considered a formed element produced in red bone marrow?

What is the process of production of formed elements called?

Which of the following is NOT a major type of lymphocyte mentioned in the text?

After being produced in the red bone marrow, where do most formed elements move directly?

What is the reason for the name 'T-lymphocytes'?

Why were B-lymphocytes given their name?

What is the primary function of the thymus?

Where do immature T-lymphocytes originate from before migrating to the thymus?

What is the primary function of red bone marrow?

What cells are primarily responsible for the maturation of T-lymphocytes within the thymus?

What structures subdivide the thymic lobes into lobules?

Which part of a thymic lobule contains immature T-lymphocytes?

What type of cells secrete thymic hormones that participate in T-lymphocyte maturation?

What term is used to describe the thymus due to its composition of lymphoid cells and epithelial tissue?

Where are the details of T-lymphocyte maturation described?

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