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Questions and Answers
What forms the stroma of endocrine glands?
What forms the stroma of endocrine glands?
Which cells are primarily found in the pars distalis of the pituitary gland?
Which cells are primarily found in the pars distalis of the pituitary gland?
How are hormone secretions primarily stored in most endocrine glands?
How are hormone secretions primarily stored in most endocrine glands?
What percentage of cells in the pars distalis are chromophobe cells?
What percentage of cells in the pars distalis are chromophobe cells?
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Which part of the pituitary gland is involved in the secretion of hormones?
Which part of the pituitary gland is involved in the secretion of hormones?
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What is the primary role of somatotropic cells in the endocrine system?
What is the primary role of somatotropic cells in the endocrine system?
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Which of the following hormones is NOT produced by basophils in the adenohypophysis?
Which of the following hormones is NOT produced by basophils in the adenohypophysis?
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Which of the following statements correctly describes the relationship between the neurohypophysis and hormones?
Which of the following statements correctly describes the relationship between the neurohypophysis and hormones?
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What distinguishes parafollicular cells from follicular cells in the thyroid gland?
What distinguishes parafollicular cells from follicular cells in the thyroid gland?
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What is the major function of vasopressin (ADH) in the body?
What is the major function of vasopressin (ADH) in the body?
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Flashcards
Endocrine System
Endocrine System
A group of ductless glands that produce hormones, which are secreted directly into the bloodstream or lymphatic system. These hormones regulate various bodily functions.
Neuroendocrine System
Neuroendocrine System
The endocrine system and nervous system work together to regulate body functions. The hypothalamus acts as a bridge between these systems.
Adenohypophysis
Adenohypophysis
The anterior lobe of the pituitary gland, responsible for producing and releasing hormones that control other endocrine glands, growth, and metabolism.
Pars Distalis
Pars Distalis
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Chromophobes
Chromophobes
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What are Acidophils?
What are Acidophils?
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What does growth hormone (somatotropin) do?
What does growth hormone (somatotropin) do?
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What is the function of prolactin (lactogenic hormone)?
What is the function of prolactin (lactogenic hormone)?
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What are Basophils?
What are Basophils?
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What is the Pars tuberalis?
What is the Pars tuberalis?
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Study Notes
Endocrine System Overview
- The endocrine system, along with the nervous system, controls bodily functions.
- It's composed of ductless glands that release hormones directly into the bloodstream or lymph.
- The hypothalamus integrates and coordinates both systems.
- Endocrine components exist in three forms: separate glands, isolated endocrine cells (APUD), and scattered masses within other glands.
General Structure of Endocrine Glands
- Endocrine glands are compact organs with both stroma (supporting tissue) and parenchyma (secreting cells).
- Stroma includes capsules, septa, and a reticular network.
- Parenchyma comprises groups of secreting cells with capillaries or sinusoids in between.
- Secretion can be stored within cells or in a central mass depending on the gland.
Hypophysis (Pituitary) Gland
- Located in the sella turcica of the sphenoid bone and weighs ~0.5g.
- Connected to the hypothalamus by the infundibular stalk.
- Stroma: Dense connective tissue and septa (pars intermedia). Reticular fibers network.
- Parenchyma (Adenohypophysis): Anterior lobe with cords of secretory cells, blood sinusoids, and fibroblasts.
- Parenchyma (Neurohypophysis): Posterior lobe containing nerve fibers, nerve endings, and glial cells.
Adenohypophysis (Anterior Pituitary)
- Consists of pars distalis, pars tuberalis, and pars intermedia.
- Pars Distalis: Largest portion (~75%), with secretory cells arranged in cords and fibroblasts. Reticular fibers support.
- Chromophobes (Chief cells): ~52%, small, round, do not stain well; may be resting or precursor to chromophils.
- Chromophils: ~48%, stain with acidic or basic dyes, and contain hormonal granules.
- Acidophils (α cells): Eosinophilic granules;
- Somatotropes: Secrete growth hormone (GH), stimulating liver production of somatomedins for bone growth.
- Lactotropes (Mammotropes): Secrete prolactin (PRL), for milk production in females (role in males unclear).
- Basophils (β cells): Basophilic granules;
- Gonadotropes: Larger than other cells;
- FSH-secreting cells: Stimulate follicle development (ovary) and spermatogenesis (testes).
- LH-secreting cells: In females, mature follicles, corpus luteum formation, and progesterone production. In males, stimulate testosterone secretion.
- Thyrotropes: Secrete Thyroid Stimulating Hormone (TSH), stimulating thyroid hormone production.
- Corticotropes: Secrete Adrenocorticotropic Hormone (ACTH), stimulating adrenal cortex growth and hormone release (cortisol, aldosterone).
- Gonadotropes: Larger than other cells;
- Acidophils (α cells): Eosinophilic granules;
- Pars Tuberalis: Funnel-shaped region surrounding the infundibulum (stalk). Highly vascularized.
Neurohypophysis (Posterior Pituitary)
- Contains pars nervosa, infundibulum, and median eminence.
- Unmyelinated axons from neurosecretory cells in the hypothalamus pass to the pars nervosa to store hormones oxytocin and vasopressin (ADH).
- Pituicytes: Glial-like cells that support the nerve fibers.
- Herring Bodies: Neurosecretory granules visible microscopically.
- Vasopressin (ADH): Promotes blood vessel contraction, increasing blood pressure, and kidney water reabsorption (reducing urine volume).
- Oxytocin: Stimulates uterine contractions during childbirth and milk ejection.
Thyroid Gland
- Located anterior to the larynx, composed of two lobes.
- Follicular cells: Cuboidal to columnar epithelium lining follicles (cavity filled with colloid).
- Parafollicular cells (C cells): Produce calcitonin, lowering blood calcium by inhibiting bone resorption.
- Thyroglobulin production: Controlled by TSH from the anterior pituitary. Thyroxine increases cellular metabolism.
- Hypothyroidism (cretinism): Dwarfism, mental retardation (childhood).
- Hyperthyroidism: Exophthalmos, goiter, overactivity.
Parathyroid Glands
- Small glands near the thyroid.
- Chief cells: Secrete parathyroid hormone (PTH), maintaining blood calcium levels.
- Oxyphil cells: Uncertain function.
- PTH: Increases osteoclast activity, bone matrix absorption, and calcium release into blood.
- Hyperparathyroidism: High blood calcium, bone demineralization, fractures.
- Hypoparathyroidism: Low blood calcium, muscle spasms (tetany).
Suprarenal (Adrenal) Glands
- Situated atop the kidneys.
- Cortex (3 zones):
- Zona glomerulosa: Secretes aldosterone, regulating sodium and potassium balance.
- Zona fasciculata: Secretes glucocorticoids, e.g., cortisol (controlling metabolism, reducing immune response).
- Zona reticularis: Secretes androgens.
- Medulla: Composed of chromaffin cells that secrete epinephrine and norepinephrine during stress responses.
Pancreatic Islets of Langerhans
- Clusters of cells within the exocrine pancreas.
- α (A) cells: Secrete glucagon, increasing blood glucose by glycogen breakdown.
- β (B) cells: Secrete insulin, promoting glucose storage.
- Δ (D) cells: Secrete somatostatin, inhibiting growth hormone secretion.
- F cells: Secrete pancreatic polypeptide, affecting gallbladder and bile release.
Pineal Body
- Located in the brain.
- Pinealocytes: Produce melatonin.
- Melatonin secretion is influenced by darkness and light; may regulate other endocrine glands and puberty.
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Description
This quiz explores the key concepts of the endocrine system, including its structures, functions, and the role of the pituitary gland. Learn about the integration of hormones and the different forms that endocrine components can take. Perfect for students studying human physiology or related fields.
