Past Questions - Endocrinology Flashcards
(12 cards)
Cells of pars distalis of adenohypophysis
Cell Organization: (of Pars DISTALIS)
1) Acidophil (70%)
1.1) Somatotropic = 50% = GH
1.2) Lactogenic = 20% = Prolactin
2) Basophil (30%)
2.1) Corticotropic = 20% = ACTH
2.2) Gonadotropic = 5% = FSH + LH
2.3) Thyrotropic = 5% = TSH
3) Chromophobe
All these cells have very developed Rough ER and secretory vesicles, because they secrete proteins.
Describe the microscopic anatomy of the cortical region of the adrenal glands
Cortical region: External layer (appears lighter), below capsule. Lipid secreting cells developed SER and lipid vacuoles. 3 Layers:
1) Zona glomerulosa (most external zona) = Aldosterone = cells are circular
2) Zona fasciculata = Glucocorticoids = network of parallel fibers
3) Zona reticularis = Androgens = network of bundles
Macroscopic anatomy of thyroid gland
Thyroid gland is located anteriorly in the neck, anterior to trachea and inferior to the larynx. Consists of two lobes connected by the isthmus. It is the only follicular gland in body.
Vascularization: Superior + Inferior Thyroid Artery. Drainage is by the Superior + Middle + Inferior Thyroid Veins
Innervation: Vagus nerve + Cervical Sympathetic Ganglia
Thyroid gland posterior relations
The posterior relations of the thyroid gland include:
- Parathyroid glands – Typically, four small parathyroid glands are embedded in the posterior surface of the thyroid gland.
- Recurrent laryngeal nerves – These nerves lie in the tracheoesophageal groove and run posterior to the thyroid gland before entering the larynx.
- Esophagus – The esophagus lies posterior to the trachea and slightly to the left side of the thyroid gland.
- Prevertebral fascia and muscles – These include the longus colli muscles, which lie posterior to the thyroid gland and separate it from the vertebral column.
This anatomical positioning is significant for surgical and clinical considerations, especially during thyroidectomy.
Vascularization of the adenohypophysis
Vascularization: Superior hypophyseal artery (collateral of Circle of Willis) reach into infundibulum and form primary plexus capillaries. Venules from these capillaries reach distalis/intermedia parts and called secondary plexus. Inferior hypophyseal vein drain blood into cavernous sinuses located laterally to the gland.
Microanatomy of the neurohypophysis
The neurohypophysis (posterior pituitary) consists of two main parts:
1. Pars nervosa: The distal portion that stores and releases hormones.
2. Infundibulum: The stalk connecting the posterior pituitary to the hypothalamus.
It consists of structures such as:
• Axons of hypothalamic neurons: These neurons extend from the hypothalamus and pass through the infundibulum into the posterior pituitary. They release antidiuretic hormone (ADH) and oxytocin.
• Pituicytes: Specialized glial cells that support the axons and store hormone granules.
• Herring bodies: Storage sites for ADH and oxytocin at the end of axons in the pars nervosa.
The neurohypophysis primarily serves to store and release hormones produced in the hypothalamus, without producing them itself.
Adrenal medulla: describe cells and innervation
Medullary region, Deeper and darker, Neural crest origin. Big cells with big nuclei, dark vesicles, stainable with Chromium salt. Stainable because of Adrenaline and Noradrenaline secretion.
Innervation: The medullary region behaves like an orthosympathetic ganglion, it receives fibers through the splanchnic nerves from thoracic spinal cord lateral horns. The medulla cells do not have axons = release neurotransmitters into blood
Describe the microscopic structure of anterior pituitary gland
The adenohypophysis (anterior pituitary) is made up of glandular epithelial tissue and is responsible for producing several important hormones. It is divided into three regions:
1. Pars Distalis: The largest portion, where most of the hormone-producing cells are located.
2. Pars Tuberalis: Surrounds the infundibulum (pituitary stalk).
3. Pars Intermedia: A thin layer between the anterior and posterior pituitary.
Cell Types
- H and E staining = Acidophil, Basophil and Chromophobe cells.
- Hormone producing cells:
Somatotropic cells, GH.
Lactotrophic cells, Prolactin.
Gonadotropic cells, FSH/LH.
Corticotropic cells, ACTH.
Thyrotropic cells, TSH.
Organization
These hormone-secreting cells are arranged in clusters or cords and are surrounded by a rich vascular network, which allows the secretion of hormones directly into the bloodstream.
Describe the macroscopic anatomy of the left adrenal gland (relations, limits and morphology).
The left adrenal gland is a triangular-shaped endocrine organ located on the superior pole of the left kidney. It is part of the endocrine system and plays a crucial role in producing hormones such as adrenaline, cortisol, and aldosterone.
Location and relations: Anteroinferiorly in relationship with pancreas, splenic artery and vein. Anterosuperiorly in indirect relationship with stomach. Medially in relationship with celiac plexus and abdominal aorta. Posteriorly rests indirectly on left lateral pillar of diaphragm.
Macroscopic anatomy of adrenal cortex
The adrenal cortex is the outer layer of the adrenal glands, responsible for producing steroid hormones like cortisol, aldosterone, and androgens. It surrounds the adrenal medulla and makes up the majority of the adrenal gland.
• Three zones:
1. Zona glomerulosa (outermost): Produces mineralocorticoids (e.g., aldosterone).
2. Zona fasciculata (middle): Produces glucocorticoids (e.g., cortisol).
3. Zona reticularis (innermost): Produces androgens (e.g., dehydroepiandrosterone, DHEA).
The adrenal cortex appears yellowish due to its high lipid content in the steroid-producing cells. It is highly vascularized to support hormone secretion.
The microscopic anatomy of the parathyroid glands
The parathyroid glands are composed of chief cells and oxyphil cells, surrounded by a delicate connective tissue capsule.
• Chief cells: Small, polygonal cells with a pale cytoplasm and round nuclei. They are responsible for secreting parathyroid hormone (PTH), which regulates calcium levels in the blood.
• Oxyphil cells: Larger cells with an eosinophilic cytoplasm due to abundant mitochondria. Their function is not well understood but may be involved in aging or metabolic support.
The gland is richly vascularized, ensuring efficient hormone secretion into the bloodstream.
Arterial supply of adrenal glands
The adrenal glands receive a rich arterial supply from three main sources on each side:
1. Superior suprarenal arteries – Branches of the inferior phrenic artery.
2. Middle suprarenal artery – A direct branch of the abdominal aorta.
3. Inferior suprarenal artery – A branch of the renal artery.
These arteries form a subcapsular plexus, which further branches into smaller arterioles supplying the adrenal cortex and medulla. The medullary arteries penetrate directly into the medulla, ensuring rapid hormone secretion into circulation.
