The Endocrine System and Pituitary Gland

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Questions and Answers

What is the main function of the endocrine system?

To regulate body temperature

To secrete hormones directly to the blood (correct)

To transmit nerve impulses

To produce digestive enzymes

Which of the following glands is part of the endocrine system?

Kidneys

Suprarenal gland (correct)

Pancreas

Liver

What is the main difference between chromophobes and chromophils?

Chromophobes have granular cytoplasm, chromophils don't

Chromophobes don't take histological stain, chromophils do (correct)

Chromophobes take histological stain, chromophils don't

Chromophobes are smaller, chromophils are larger

Which cells in the pars distalis produce growth hormone?

Somatotrophs Signup and view all the answers

What is the function of the posterior lobe of the pituitary gland?

To store and release neurosecretory material Signup and view all the answers

What is the characteristic of the cells in the pars nervosa?

They are lightly stained and composed of a few cells and nerve fibers Signup and view all the answers

What is the name of the hormone produced by lactotrophs?

Prolactin Signup and view all the answers

What is the characteristic of the cells in the pars intermedia?

They are arranged in follicles or cords and have blood vessels in between Signup and view all the answers

What is the function of the cells in the zona glomerulosa of the adrenal cortex?

Secretion of mineralocorticoids Signup and view all the answers

What type of cells are found in the pituitary gland?

All of the above Signup and view all the answers

What is the function of the principal cells in the thyroid gland?

Secretion of thyroid hormones Signup and view all the answers

What is the location of the Herring bodies in the pituitary gland?

Along the nerve fibers Signup and view all the answers

What is the function of the C cells in the thyroid gland?

Secretion of thyrocalcitonin hormone Signup and view all the answers

What is the characteristic of the cells in the zona fasciculata of the adrenal cortex?

Large polyhedral cells with acidophilic vacuolated cytoplasm Signup and view all the answers

What is the location of the pituicytes in the pituitary gland?

Few in number and scattered throughout the gland Signup and view all the answers

What is the characteristic of the zona reticularis of the adrenal cortex?

Small polyhedral cells with less vacuolated cytoplasm Signup and view all the answers

Study Notes

The Endocrine System

The endocrine system secretes hormones directly into the blood, including the pituitary gland, thyroid gland, and suprarenal gland.

The Pituitary Gland

The pituitary gland has anterior and posterior lobes.
The anterior lobe consists of:
- Pars distalis
- Pars intermedia
- Pars tuberalis
The posterior lobe (neurohypophysis) consists of:
- Pars nervosa
Pars distalis:
- Surrounded by a thin CT capsule
- Consists of irregular cords of cells with numerous fenestrated capillaries
- Cells of Pars distalis:
  - Chromophobes (52%): smaller, non-granular cytoplasm, don't take histological stain
  - Chromophils (48%): larger, granular cytoplasm, take histological stain
- Chromophils:
  - Acidophil cells (37%): moderate in size, have acidophilic granules, secrete somatotrophs (Growth Hormone, GH)
  - Basophil cells (11%): larger in size, have basophilic granules, secrete thyrotrophs (Thyroid Stimulating Hormone, TSH)
  - Lactotrophs: secrete prolactin
  - Gonadotrophs: secrete Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
  - Corticotrophs: secrete Adrenocorticotrophic Hormone (ACTH)
Pars intermedia:
- Separated from Pars distalis by a thin, incomplete cleft
- Cells arranged in follicles or cords with blood vessels in between
Pars nervosa:
- Lightly stained due to few cells and mainly nerve fibers
- Nerve fibers carry neurosecretory material from the hypothalamic nuclei
- Neurosecretions (vasopressin and oxytocin) are stored in Herring bodies
- Few cells, "pituicytes", are neuroglial cells
- Rich blood capillaries

The Thyroid Gland

The thyroid gland is surrounded by a CT capsule, which sends septa to divide the gland into indistinct lobules
The parenchyma is formed of follicles, which are filled with acidophilic colloid
Lining epithelium varies from flat to columnar
Two types of cells are present:
- Follicular cells (principal cells): main type of cells, secrete thyroid hormones (T3 & T4), cuboidal, columnar, or squamous
- Parafollicular cells (C cells): secrete thyrocalcitonin hormone, larger in size, don't reach the follicular cavity
Blood capillaries are found between the follicles

The Suprarenal Gland

Each gland has an outer cortex and an inner medulla
The adrenal cortex:
- Zona glomerulosa: a narrow zone under the capsule, formed of columnar acidophilic cells, secretes mineralocorticoids (aldosterone)
- Zona fasciculata: the middle zone, formed of large polyhedral cells with acidophilic vacuolated cytoplasm, secretes glucocorticoid
- Zona reticularis: the inner zone, formed of small polyhedral cells with less vacuolated cytoplasm, secretes sex hormones and some glucocorticoids