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BSC NURSING SEM1 APPLIED ANATOMY UNIT 5 The Endocrine system

  • Structure of Hypothalamus

Structure of the Hypothalamus

The hypothalamus is a vital part of the diencephalon, located at the base of the brain below the thalamus and above the pituitary gland. It plays a crucial role in maintaining homeostasis and regulating various physiological processes.

Anatomical Structure

  1. Location:
    • Situated in the brain’s ventral part.
    • Lies below the thalamus and forms the floor and part of the lateral walls of the third ventricle.
  2. Divisions:
    • The hypothalamus is divided into three major regions based on their anterior-posterior position:
      • Anterior region (Preoptic and Supraoptic region):
        • Contains nuclei like the supraoptic nucleus, paraventricular nucleus, and preoptic nucleus.
      • Middle region (Tuberal region):
        • Includes the arcuate nucleus, ventromedial nucleus, and dorsomedial nucleus.
      • Posterior region (Mammillary region):
        • Contains the mammillary bodies and posterior hypothalamic nucleus.
  3. Functional Zones:
    • The hypothalamus is also organized into medial, lateral, and periventricular zones:
      • Medial zone: Controls autonomic and endocrine functions.
      • Lateral zone: Contains the medial forebrain bundle and regulates appetite and wakefulness.
      • Periventricular zone: Involved in neuroendocrine functions.
  4. Connections:
    • Afferent connections: Receives inputs from the limbic system, cerebral cortex, brainstem, and spinal cord.
    • Efferent connections: Sends outputs to the pituitary gland, autonomic nervous system, and other brain regions.

Major Nuclei of the Hypothalamus

  1. Supraoptic and Paraventricular Nuclei:
    • Regulate water balance via antidiuretic hormone (ADH).
    • Involved in oxytocin release.
  2. Arcuate Nucleus:
    • Plays a role in feeding, energy balance, and neuroendocrine function.
  3. Ventromedial and Lateral Hypothalamic Nuclei:
    • Ventromedial nucleus: Satiety center.
    • Lateral hypothalamic area: Hunger center.
  4. Mammillary Bodies:
    • Involved in memory processing.
  5. Preoptic Area:
    • Regulates thermoregulation and reproductive behaviors.

Blood Supply

  • Arterial supply:
    • Supplied by branches of the circle of Willis, including the anterior cerebral artery, posterior cerebral artery, and posterior communicating artery.
  • Venous drainage:
    • Drains into the internal cerebral veins and cavernous sinus.

Clinical Significance

  1. Disorders of the hypothalamus can lead to:
    • Endocrine dysfunctions (e.g., diabetes insipidus, hypopituitarism).
    • Behavioral changes (e.g., hyperphagia or anorexia).
    • Sleep and thermoregulation disorders.
  2. Lesions:
    • Tumors (e.g., craniopharyngiomas) or trauma may compress the hypothalamus, affecting its function.
  • Pineal Gland

Pineal Gland

The pineal gland is a small, pea-shaped endocrine gland located in the brain. It plays a crucial role in regulating circadian rhythms and the production of melatonin, which influences sleep-wake cycles.

Anatomical Structure

  1. Location:
    • Situated in the epithalamus, between the two hemispheres of the brain.
    • Lies in a groove where the two halves of the thalamus join.
  2. Shape and Size:
    • Resembles a small pine cone (hence the name “pineal”).
    • Measures approximately 5–8 mm in length and weighs about 0.1–0.2 grams.
  3. Histology:
    • Composed of two main cell types:
      • Pinealocytes:
        • Specialized secretory cells responsible for melatonin production.
        • Contain large, round nuclei and long cytoplasmic processes.
      • Glial cells:
        • Supportive cells that provide structural and metabolic support.
    • Contains calcium deposits (corpora arenacea or “brain sand”), which increase with age.

Functions

  1. Melatonin Production:
    • Secretes melatonin, a hormone that regulates sleep-wake cycles.
    • Production is influenced by the light-dark cycle:
      • Increased in darkness.
      • Decreased in light.
  2. Regulation of Circadian Rhythms:
    • Acts as a biological clock, coordinating the body’s internal timing mechanisms.
  3. Role in Puberty:
    • Thought to inhibit the premature onset of puberty by regulating gonadotropin release.
  4. Antioxidant Effects:
    • Melatonin acts as a free radical scavenger, protecting cells from oxidative stress.

Connections

  1. Afferent Inputs:
    • Receives signals from the retina via the retinohypothalamic tract.
    • Light information is processed by the suprachiasmatic nucleus of the hypothalamus and relayed to the pineal gland via sympathetic innervation.
  2. Efferent Outputs:
    • Releases melatonin into the bloodstream and cerebrospinal fluid to influence distant target organs.

Blood Supply

  1. Arterial Supply:
    • Mainly supplied by branches of the posterior cerebral artery, particularly the posterior choroidal arteries.
  2. Venous Drainage:
    • Drains into the great cerebral vein of Galen.

Clinical Significance

  1. Pineal Tumors:
    • Rare but may cause symptoms such as headache, hydrocephalus, or vision problems due to compression of nearby structures.
  2. Sleep Disorders:
    • Dysfunction of melatonin production can lead to conditions such as insomnia or seasonal affective disorder (SAD).
  3. Calcification:
    • The pineal gland often calcifies with age, which is typically benign but can be observed on imaging.
  4. Endocrine Disruptions:
    • May affect reproductive hormones and contribute to delayed or precocious puberty.

Interesting Facts

  • The pineal gland has been referred to as the “third eye” in various philosophical and spiritual traditions, due to its central location and sensitivity to light.
  • Pituitary gland

Pituitary Gland (Hypophysis)

The pituitary gland, also known as the master gland, is a pea-shaped endocrine organ located at the base of the brain. It plays a critical role in regulating various physiological processes by secreting hormones that control other endocrine glands and body functions.

Anatomical Structure

  1. Location:
    • Situated in the sella turcica, a bony depression of the sphenoid bone.
    • Connected to the hypothalamus by the infundibulum (pituitary stalk).
  2. Parts:
    • Divided into two main lobes with distinct embryological origins and functions:
      • Anterior Pituitary (Adenohypophysis):
        • Constitutes about 75% of the gland.
        • Develops from Rathke’s pouch (oral ectoderm).
        • Subdivided into:
          • Pars distalis (main functional part).
          • Pars intermedia (remnant in humans, secretes minimal hormones).
          • Pars tuberalis (surrounds the infundibulum).
      • Posterior Pituitary (Neurohypophysis):
        • Constitutes about 25% of the gland.
        • Develops from the neural ectoderm of the diencephalon.
        • Includes:
          • Pars nervosa (main functional part).
          • Infundibulum.

Histological Structure

  1. Anterior Pituitary:
    • Composed of endocrine cells organized into cords and clusters.
    • Contains five hormone-secreting cell types:
      • Somatotrophs: Secrete growth hormone (GH).
      • Lactotrophs: Secrete prolactin (PRL).
      • Gonadotrophs: Secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
      • Thyrotrophs: Secrete thyroid-stimulating hormone (TSH).
      • Corticotrophs: Secrete adrenocorticotropic hormone (ACTH).
  2. Posterior Pituitary:
    • Contains non-myelinated axons of hypothalamic neurons (from the supraoptic and paraventricular nuclei).
    • Stores and releases:
      • Antidiuretic hormone (ADH) (vasopressin).
      • Oxytocin.

Functions

  1. Hormones of the Anterior Pituitary:
    • Growth Hormone (GH): Stimulates growth, protein synthesis, and cell regeneration.
    • Prolactin (PRL): Promotes lactation.
    • Adrenocorticotropic Hormone (ACTH): Stimulates cortisol release from the adrenal cortex.
    • Thyroid-Stimulating Hormone (TSH): Stimulates thyroid gland activity.
    • Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH): Regulate reproductive processes.
  2. Hormones of the Posterior Pituitary:
    • ADH: Regulates water balance by promoting water reabsorption in the kidneys.
    • Oxytocin: Facilitates uterine contractions during labor and milk ejection during breastfeeding.

Blood Supply

  1. Arterial Supply:
    • Supplied by branches of the internal carotid artery:
      • Superior hypophyseal artery: Supplies the anterior pituitary and infundibulum.
      • Inferior hypophyseal artery: Supplies the posterior pituitary.
  2. Venous Drainage:
    • Drains into the cavernous sinus via hypophyseal veins.
  3. Portal System:
    • The hypophyseal portal system connects the hypothalamus to the anterior pituitary, allowing hypothalamic hormones to regulate pituitary activity.

Clinical Significance

  1. Disorders of the Pituitary Gland:
    • Hypersecretion:
      • Acromegaly (GH excess in adults).
      • Gigantism (GH excess in children).
      • Cushing’s disease (ACTH overproduction).
    • Hyposecretion:
      • Dwarfism (GH deficiency in children).
      • Hypopituitarism (deficiency of one or more pituitary hormones).
  2. Pituitary Tumors:
    • Commonly adenomas, which can cause hormonal imbalances or compress nearby structures like the optic chiasm, leading to bitemporal hemianopia.
  3. Diabetes Insipidus:
    • Caused by insufficient ADH secretion, leading to excessive urination and thirst.
  4. Syndrome of Inappropriate ADH Secretion (SIADH):
    • Excess ADH causing water retention and hyponatremia.

Interesting Facts

  • The pituitary gland is often called the “master gland” because it regulates the function of other endocrine glands like the thyroid, adrenal glands, and gonads.
  • Despite its small size (~0.5 grams in adults), it exerts control over numerous critical body functions.
  • Thyroid,

Thyroid Gland

The thyroid gland is a butterfly-shaped endocrine gland located in the neck. It plays a critical role in metabolism, growth, and development by producing thyroid hormones.

Anatomical Structure

  1. Location:
    • Situated in the anterior neck, spanning the C5 to T1 vertebral levels.
    • Lies anterior to the trachea and just below the larynx.
  2. Shape and Size:
    • Composed of two lateral lobes connected by a thin isthmus.
    • Average weight is 20–30 grams in adults.
    • Occasionally, a pyramidal lobe extends upward from the isthmus.
  3. Capsule:
    • Enclosed by a fibrous capsule, which is surrounded by the pretracheal fascia.
  4. Relations:
    • Anterior: Covered by skin, platysma, and infrahyoid muscles.
    • Posterior: Related to the trachea and esophagus.
    • Lateral: Adjacent to the carotid sheath (contains the carotid artery, internal jugular vein, and vagus nerve).
    • Superior: Close to the larynx.
    • Inferior: Extends toward the thoracic inlet.

Histological Structure

  1. Thyroid Follicles:
    • Functional units of the thyroid gland.
    • Composed of a single layer of follicular cells surrounding a central lumen filled with colloid (contains thyroglobulin, a precursor to thyroid hormones).
  2. Cell Types:
    • Follicular cells:
      • Synthesize thyroxine (T4) and triiodothyronine (T3).
    • Parafollicular cells (C cells):
      • Produce calcitonin, a hormone involved in calcium homeostasis.

Functions

  1. Thyroid Hormones:
    • T4 (Thyroxine):
      • Major circulating hormone.
      • Acts as a prohormone and is converted to T3 in peripheral tissues.
    • T3 (Triiodothyronine):
      • Active form of the hormone.
      • Regulates metabolic rate, protein synthesis, and growth.
    • These hormones influence:
      • Basal metabolic rate.
      • Body temperature regulation.
      • Development of the central nervous system in fetuses and infants.
      • Cardiovascular function.
  2. Calcitonin:
    • Reduces blood calcium levels by inhibiting bone resorption and promoting calcium deposition in bones.

Blood Supply

  1. Arterial Supply:
    • Superior thyroid artery (branch of the external carotid artery).
    • Inferior thyroid artery (branch of the thyrocervical trunk of the subclavian artery).
  2. Venous Drainage:
    • Superior thyroid vein and middle thyroid vein (drain into the internal jugular vein).
    • Inferior thyroid vein (drains into the brachiocephalic vein).
  3. Lymphatic Drainage:
    • Drains into the prelaryngeal, pretracheal, and paratracheal lymph nodes.

Regulation of Thyroid Function

  1. Hypothalamic-Pituitary-Thyroid Axis:
    • The hypothalamus secretes thyrotropin-releasing hormone (TRH).
    • TRH stimulates the anterior pituitary to release thyroid-stimulating hormone (TSH).
    • TSH stimulates the thyroid gland to produce T3 and T4.
    • Negative feedback: High levels of T3 and T4 inhibit TRH and TSH secretion.

Clinical Significance

  1. Thyroid Disorders:
    • Hypothyroidism:
      • Underactive thyroid gland leading to low levels of T3 and T4.
      • Symptoms: Fatigue, weight gain, cold intolerance, dry skin, bradycardia, and constipation.
      • Common causes: Hashimoto’s thyroiditis, iodine deficiency.
    • Hyperthyroidism:
      • Overactive thyroid gland causing excessive T3 and T4 production.
      • Symptoms: Weight loss, heat intolerance, tachycardia, tremors, and exophthalmos.
      • Common causes: Graves’ disease, toxic multinodular goiter.
    • Goiter:
      • Enlargement of the thyroid gland, which can occur in hypo-, hyper-, or euthyroid states.
    • Thyroid Nodules:
      • Focal lesions in the thyroid, which may be benign or malignant.
    • Thyroid Cancer:
      • Types: Papillary, follicular, medullary, and anaplastic carcinoma.
  2. Thyroid Function Tests:
    • T3, T4, and TSH levels: Used to diagnose thyroid dysfunction.
    • Anti-thyroid antibodies: Help diagnose autoimmune thyroid diseases (e.g., Hashimoto’s or Graves’).

Interesting Facts

  • The thyroid gland is the first endocrine gland to develop in the fetus (around the 4th week of gestation).
  • It stores hormones in large quantities, sufficient for several weeks of activity.
  • Parathyroid

Parathyroid Glands

The parathyroid glands are small, pea-shaped endocrine glands located on the posterior surface of the thyroid gland. Their primary function is to regulate calcium and phosphate levels in the blood and bone through the secretion of parathyroid hormone (PTH).

Anatomical Structure

  1. Location:
    • Typically, four parathyroid glands are present (two superior and two inferior).
    • Located on the posterior aspect of the thyroid gland, embedded within its capsule.
  2. Shape and Size:
    • Oval or round in shape.
    • Each gland measures about 3–5 mm in diameter and weighs approximately 30–50 mg.
  3. Variation:
    • The number and location of parathyroid glands can vary.
    • Ectopic glands may be found in the mediastinum, near the thymus, or along the carotid sheath.

Histological Structure

  1. Cell Types:
    • Chief cells (Principal cells):
      • Most abundant.
      • Secrete parathyroid hormone (PTH).
    • Oxyphil cells:
      • Larger cells with an unknown precise function.
      • Increase in number with age.
  2. Capsule:
    • Each gland is surrounded by a thin fibrous capsule.
    • Septa extend from the capsule into the gland, dividing it into lobules.

Functions

  1. Parathyroid Hormone (PTH):
    • A key regulator of calcium and phosphate homeostasis.
    • Effects of PTH:
      • Bone: Stimulates osteoclast activity, increasing calcium and phosphate release into the blood.
      • Kidneys:
        • Increases calcium reabsorption.
        • Decreases phosphate reabsorption.
        • Stimulates the production of active vitamin D (calcitriol).
      • Intestines: Indirectly increases calcium absorption by enhancing vitamin D activation.
  2. Calcium Regulation:
    • PTH works in conjunction with calcitonin (from the thyroid gland) and vitamin D to maintain calcium levels within a narrow range.

Blood Supply

  1. Arterial Supply:
    • Supplied by branches of the inferior thyroid artery.
    • Occasionally, additional blood supply is provided by the superior thyroid artery or other nearby arteries.
  2. Venous Drainage:
    • Drains into the thyroid veins, which subsequently empty into the internal jugular and brachiocephalic veins.
  3. Lymphatic Drainage:
    • Drains into the deep cervical lymph nodes and paratracheal lymph nodes.

Regulation of Parathyroid Function

  1. Calcium Levels:
    • Low blood calcium levels stimulate PTH secretion.
    • High blood calcium levels inhibit PTH secretion.
  2. Negative Feedback:
    • PTH secretion is inhibited by elevated levels of calcium and active vitamin D (calcitriol).

Clinical Significance

  1. Hyperparathyroidism:
    • Primary hyperparathyroidism:
      • Caused by adenomas, hyperplasia, or carcinoma of the parathyroid glands.
      • Leads to hypercalcemia, causing symptoms like kidney stones, bone pain, and abdominal discomfort.
    • Secondary hyperparathyroidism:
      • Caused by chronic hypocalcemia due to vitamin D deficiency, renal failure, or malabsorption.
    • Tertiary hyperparathyroidism:
      • Occurs after prolonged secondary hyperparathyroidism, with autonomous PTH secretion.
  2. Hypoparathyroidism:
    • Often results from surgical removal of the parathyroid glands during thyroid surgery.
    • Leads to hypocalcemia, causing symptoms like tetany, muscle cramps, and cardiac arrhythmias.
  3. Parathyroid Tumors:
    • Parathyroid adenomas are the most common cause of primary hyperparathyroidism.
  4. Parathyroid Disorders and Bone Health:
    • Excess PTH can lead to osteitis fibrosa cystica, a condition where bones become weak and deformed.

Diagnostic Tests

  1. Serum Tests:
    • PTH levels, calcium, phosphate, and vitamin D levels are assessed to diagnose parathyroid disorders.
  2. Imaging:
    • Ultrasound, CT scan, or Sestamibi scan can locate abnormal or ectopic parathyroid glands.
  3. Bone Density Test:
    • Used to assess the impact of parathyroid disorders on bone health.
  • Thymus,

Thymus Gland

The thymus gland is a specialized organ of the immune system, primarily responsible for the maturation and differentiation of T-lymphocytes (T-cells), which play a crucial role in adaptive immunity. It is most active during childhood and undergoes gradual involution with age.

Anatomical Structure

  1. Location:
    • Situated in the anterior part of the superior mediastinum, extending into the anterior mediastinum.
    • Positioned posterior to the sternum and anterior to the heart and great vessels (e.g., aorta).
  2. Shape and Size:
    • Bilobed, pyramid-shaped structure.
    • In children, it weighs approximately 10–15 grams and can grow up to 30–40 grams during puberty.
    • After puberty, it undergoes involution, shrinking and being replaced by adipose tissue.
  3. Relations:
    • Anterior: Sternum and costal cartilages.
    • Posterior: Pericardium, great vessels (e.g., superior vena cava, aortic arch).
    • Lateral: Lungs and pleura.

Histological Structure

  1. Capsule:
    • Enclosed by a thin connective tissue capsule, which sends septa inward to divide the gland into lobules.
  2. Lobules:
    • Each lobule has two distinct regions:
      • Cortex:
        • Outer dark-staining region.
        • Contains densely packed immature T-lymphocytes (thymocytes).
      • Medulla:
        • Inner light-staining region.
        • Contains fewer, mature T-lymphocytes and unique structures called Hassall’s corpuscles.
  3. Hassall’s Corpuscles:
    • Concentric, keratinized epithelial cells found in the medulla.
    • Their precise function is unclear but may be involved in T-cell development.
  4. Epithelial Reticular Cells:
    • Provide structural support and create a microenvironment for T-cell maturation.
    • Secrete cytokines and other factors essential for T-cell differentiation.

Functions

  1. T-Cell Maturation:
    • Precursor T-cells (progenitors) from the bone marrow migrate to the thymus, where they undergo differentiation and maturation into:
      • Helper T-cells (CD4+ T-cells).
      • Cytotoxic T-cells (CD8+ T-cells).
  2. Positive and Negative Selection:
    • Ensures that only functional T-cells capable of recognizing self-MHC molecules survive (positive selection).
    • Eliminates T-cells that strongly react to self-antigens to prevent autoimmunity (negative selection).
  3. Immune Regulation:
    • The thymus helps establish self-tolerance and prevents autoimmune diseases.
  4. Hormone Secretion:
    • Produces hormones like thymosin, thymopoietin, and thymulin, which aid in T-cell development and immune function.

Blood Supply

  1. Arterial Supply:
    • Supplied by branches of the internal thoracic artery, inferior thyroid artery, and occasionally other nearby arteries.
  2. Venous Drainage:
    • Drains into the left brachiocephalic vein, internal thoracic veins, and sometimes the thyroid veins.
  3. Lymphatic Drainage:
    • Drains into the anterior mediastinal and tracheobronchial lymph nodes.

Development and Involution

  1. Embryological Development:
    • Derived from the third pharyngeal pouch during embryogenesis.
    • Begins functioning around the 12th week of gestation.
  2. Involution:
    • Active during fetal life and early childhood.
    • After puberty, the thymus gradually shrinks and is replaced by adipose and fibrous tissue.
    • Functional capacity decreases with age but continues low-level T-cell production throughout life.

Clinical Significance

  1. Thymic Disorders:
    • Thymic Hyperplasia:
      • Enlargement of the thymus, often associated with autoimmune diseases like myasthenia gravis.
    • Thymoma:
      • A tumor of the thymus, which can be benign or malignant.
      • Often associated with paraneoplastic syndromes like myasthenia gravis or pure red cell aplasia.
  2. DiGeorge Syndrome:
    • Congenital disorder caused by a defect in the development of the third pharyngeal pouch.
    • Leads to thymic hypoplasia or aplasia, resulting in severe immunodeficiency.
  3. Autoimmune Diseases:
    • Dysfunction in thymic T-cell selection can lead to autoimmunity (e.g., systemic lupus erythematosus).
  4. Thymectomy:
    • Surgical removal of the thymus, often performed in patients with myasthenia gravis or thymomas.
  • Pancreas and Adrenal glands

Pancreas

The pancreas is a dual-function gland that plays a crucial role in digestion (exocrine function) and blood glucose regulation (endocrine function).

Anatomical Structure

  1. Location:
    • Situated in the retroperitoneal space of the abdomen.
    • Lies posterior to the stomach and extends from the duodenum (right) to the spleen (left).
  2. Parts:
    • Head: Lies within the curve of the duodenum.
    • Uncinate process: A small projection from the head.
    • Neck: Narrow area connecting the head and body.
    • Body: Extends across the midline.
    • Tail: Ends near the spleen.
  3. Relations:
    • Posterior: Inferior vena cava, aorta, and left kidney.
    • Anterior: Stomach and transverse colon.

Histological Structure

  1. Exocrine Component:
    • Consists of acinar cells, which produce digestive enzymes (amylase, lipase, and proteases).
    • Enzymes are secreted into the pancreatic ducts and ultimately into the duodenum.
  2. Endocrine Component:
    • Composed of clusters of cells called the Islets of Langerhans, which secrete hormones:
      • Alpha cells: Secrete glucagon (raises blood glucose).
      • Beta cells: Secrete insulin (lowers blood glucose).
      • Delta cells: Secrete somatostatin (inhibits insulin and glucagon).
      • PP cells: Secrete pancreatic polypeptide.

Functions

  1. Exocrine Function:
    • Produces digestive enzymes and bicarbonate to neutralize stomach acid in the duodenum.
  2. Endocrine Function:
    • Maintains blood glucose levels through insulin and glucagon secretion.

Blood Supply

  1. Arterial Supply:
    • Supplied by branches of the celiac trunk and superior mesenteric artery.
      • Pancreaticoduodenal arteries (from the gastroduodenal and superior mesenteric arteries).
      • Splenic artery branches.
  2. Venous Drainage:
    • Drains into the portal vein via the splenic vein and superior mesenteric vein.

Clinical Significance

  1. Diabetes Mellitus:
    • Caused by insulin deficiency (Type 1) or insulin resistance (Type 2).
  2. Pancreatitis:
    • Inflammation of the pancreas, often caused by gallstones or alcohol.
  3. Pancreatic Cancer:
    • Frequently occurs in the head of the pancreas and may cause jaundice.

Adrenal Glands

The adrenal glands are paired endocrine organs located on top of each kidney. They produce hormones essential for stress response, metabolism, and electrolyte balance.

Anatomical Structure

  1. Location:
    • Retroperitoneal, situated above each kidney.
    • Enclosed within the renal fascia.
  2. Shape and Size:
    • Right gland: Pyramid-shaped.
    • Left gland: Crescent-shaped.
    • Each gland weighs approximately 4–6 grams.
  3. Divisions:
    • Cortex (outer region): Produces steroid hormones.
    • Medulla (inner region): Produces catecholamines.

Histological Structure

  1. Cortex:
    • Derived from mesoderm and divided into three zones:
      • Zona Glomerulosa: Produces mineralocorticoids (e.g., aldosterone).
      • Zona Fasciculata: Produces glucocorticoids (e.g., cortisol).
      • Zona Reticularis: Produces androgens (e.g., dehydroepiandrosterone).
  2. Medulla:
    • Derived from neural crest cells.
    • Contains chromaffin cells, which secrete catecholamines (epinephrine and norepinephrine).

Functions

  1. Adrenal Cortex:
    • Aldosterone: Regulates sodium and potassium balance, thus maintaining blood pressure.
    • Cortisol: Manages stress response, glucose metabolism, and anti-inflammatory actions.
    • Androgens: Precursors for sex hormones.
  2. Adrenal Medulla:
    • Epinephrine and Norepinephrine:
      • Fight-or-flight response.
      • Increase heart rate, blood pressure, and blood glucose.

Blood Supply

  1. Arterial Supply:
    • Supplied by three arteries:
      • Superior suprarenal arteries (from the inferior phrenic artery).
      • Middle suprarenal artery (from the abdominal aorta).
      • Inferior suprarenal artery (from the renal artery).
  2. Venous Drainage:
    • Right adrenal vein drains into the inferior vena cava.
    • Left adrenal vein drains into the renal vein.

Clinical Significance

  1. Adrenal Insufficiency:
    • Primary (Addison’s disease): Caused by autoimmune destruction of the adrenal cortex.
    • Secondary: Due to insufficient ACTH secretion.
  2. Hyperfunction:
    • Cushing’s Syndrome: Excess cortisol production.
    • Conn’s Syndrome: Excess aldosterone production.
    • Pheochromocytoma: Catecholamine-secreting tumor of the adrenal medulla.
  3. Congenital Adrenal Hyperplasia:
    • Genetic disorder affecting cortisol synthesis, leading to androgen overproduction.

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Categorized as BS NURSING SEM 1 ANATOMY, Uncategorised