Endocrine Glands Flashcards
What are the main functions of the endocrine system
- Maintain body homeostasis
- Help the body to react to stress in concert with the nervous system
- Regulate growth and development
How does the endocrine system complete its functions
Through the synthesis and secretion of hormones (chemical messengers)
What are the 4 main types of hormone
- Protein and glycoprotein
- Small peptide
- Derivatives of amino acids
- Derivatives from cholesterol
What is the origin of most endocrine tissue
Epithelial origin
Name some of the major endocrine glands
- Pituitary gland
- Hypothalamus
- Pineal gland
- Thyroid gland
- Parathyroid glands
- Thymus
- Adrenal gland
- Pancreas
- Gonads (testis and ovaries)
What does the endocrine system consist of
- Major endocrine organs (thyroid gland)
- Organs with partial endocrine function (pancreas)
- Diffuse organ system: scattered cells within organs that fulfill an endocrine function (enteroendocrine cells of the gut)
Why is the pituitary gland named the ‘master gland’
Its hormones regulate the activity of many other endocrine glands
Where is the pituitary gland located
It sits in sella turica of the sphenoid bone, just below the hypothalamus
Describe the composition of the pituitary gland
Composed of two lobes:
- Anterior lobe (adenohypophysis)
- Posterior lobe (neurohypophysis)
What does the neurohypophysis develop from, and what does it stay connected to
Downward growth of the hypothalamus and stays attached to the hypothalamus by the pituitary stalk
What does the adenohypophysis develop from
Upward pocket of epithelium in the roof of the oral cavity called Rathke’s pouch
Name the hormones that are secreted from the posterior pituitary
- Oxytocin
2. Antiruietic hormone (ADH)
Name the hormones that are secreted from the anterior pituitary
- Growth hormone
- Prolactin
- LH and FSH
- Adrenocorticotropic hormone (ACTH)
- Thyroid-stimulating hormone (TSH)
What controls the hormone secretion from the anterior pituitary, and how does it reach it
The hypothalamus via the hypothalamic-hypophyseal portal system
Name the 5 cell types of the anterior pituitary and the hormones they produce
- Somatotrophs (GH)
- Thyrotrophs (TSH)
- Corticotrophs (ACTH)
- Lactotrophs (prolactin)
- Gonadotrophs (LH and FSH)
Name the 3 secretory cells of the anterior pituitary
- Acidophils
- Basophils
- Chromophobes
1 and 2 are called chromophils
Describe the structure of the anterior pituitary
Packed secretory cells interspersed with fenestrated endothelium-lined vascular sinuses
Of the 5 cell types of the anterior pituitary, state what type of secretory cell they are
- Somatotrophs (acidophil)
- Thyrotrophs (basophil)
- Corticotrophs (basophil)
- Lactotrophs (acidophil)
- Gonadotrophs (basophil)
What does the posterior pituitary consist of
The axons and nerve cells in the supraoptic and paraventricular nuclei of the hypothalamus
Name the special glial cells located in the posterior pituitary
Pituicytes
What represent aggregations of oxytocin or vasopressin in the posterior pituitary
Swellings in the axons called Herring bodies
What is the pars intermedia
The portion of the anterior lobe bordering the posterior lobe
Describe the arrangement of the thyroid gland
Two large lateral lobes connected by an isthmus, a thin band of thyroid tissue
Describe the functional unit of the thyroid gland
A thyroid follicle is a spherical space lined by epithelial cells that are low cuboidal when inactive (columnar when active)
What do T3 and T4 regulate
- Cell metabolism rate
- Heat production
- Minor role in development and growth
What are the main hormones of the thyroid gland
- Triiodothyronine (T3)
2. Tetraiodothyronine (T4)
Where are C cells found
Parafollicular cells are found adjacent to the follicular cells, in the basal lamina surrounding the follicle
What do C cells secrete
Calcitonin
What is the function of calcitonin
Inhibits osteoclast activity and lowers blood calcium
How many parathyroid glands do we have
Using 4: 2 superior and 2 inferior
What do the parathyroid glands secrete
The parathyroid hormone, a polypeptide hormone necessary for life
What is the function of the parathyroid hormone
It increases serum calcium by:
- Stimulating release of calcium from bone
- Increasing renal calcium reabsorption
- Increasing calcium absorption from the gut
Describe the 3 cells of the parathyroid glands
- Chief cells (secrete PTH)
- Oxyphils
- Adipose cells
How many islets of Langerhans exist in the pancreas, and what proportion of the pancreas do they make up
1-3 million but they only occupy 1-2% of the volume of the pancreas
What is the function of the testes
- Production of spermatozoa
2. Secretion of the male sex hormone, testosterone
What cells secrete testosterone
The Leydig cells, in the interstices between the seminiferous tubules
What is the function of the ovaries
- Produce ova
2. Secrete the female sex hormones: oestrogen, and progesterone
How is oestrogen produced
Cells of the theca interna will produce precursors which are converted to oestrogen by granulosa cells
Describe the structure of the adrenal glands
Cortex = formed of epithelial cells Medulla = formed of neural crest cells
Name the layers of the adrenal cortex (from outer to inner)
- Zona glomerulosa
- Zona fasciulata
- Zona reticularis
Name the 3 types of cholesterol-based steroid hormones the adrenal cortex secretes, and where they are produced
- Mineralocorticoids (zona glomerulosa)
- Glucocorticoids (zona fasciulata)
- Sex hormones (zona reticularis)
What do mineralocorticoids secrete
Principally aldosterone which promotes Na+ retention in the distal convoluted tubules of the kidney
What do glucocorticoids secrete
Cortisol which is involved in many aspects of metabolism (raising blood glucose etc.)
What do the sex hormones of the zona reticularis secrete
Small amounts of a variety of androgens, as well as some glucocorticoids
What does do the adrenal medulla contain, and thus secrete
Granules of adrenaline and noradrenaline that are released into the blood in response to sympathetic stimulation
What are the 3 principle cell types in the pancreatic islets
- Insulin secreting cells (70%)
- Glucagon secreting cells (20%)
- Somatostatin (about 5-10%)
