Histology of Endocrine Organs

Question 1

Endocrine Gland Organization

• _ cells (lacking free surface) arranged as _/_ and some as isolated individual cells
• Derived from epithelia
• Well vascularized - vessels often have _ endothelium

Answer 1

Endocrine Gland Organization

• Epithelioid cells (lacking free surface) arranged as Cords/Follicles and some as isolated individual cells
• Derived from epithelia
• Well vascularized - vessels often have Fenestrated endothelium

Question 2

Anatomy of Pituitary Gland

• Anterior pituitary ( _ ) constitutes 80% of gland - comprised of _ epithelial cells controlled by _ released from hypothalamus
• Posterior pituitary ( _ ) comprised of axons from hypothalamus and support cells
  
  • Axons carry _ and _ for storage and release

Answer 2

Anatomy of Pituitary Gland

• Anterior pituitary (Adenohypophysis) constitutes 80% of gland - comprised of Glandular epithelial cells controlled by Neurohormones released from hypothalamus
• Posterior pituitary (Neurohypophysis) comprised of axons from hypothalamus and support cells
  
  • Axons carry ADH and Oxytocin for storage and release

Question 3

Microscopic Appearance of Pituitary

Question 4

Major Cell Types in Anterior Pituitary

• _ cells - secrete GH
• _ cells - secrete TSH regulating thyroid gland secretion
• _ cells - secrete ACTH and MSH
  
  • ACTH stimulates adrenal cortex to secrete stress-related hormones and mediate metabolism
  • MSH stimulates melanocytes to produce melanin
• _ cells - secrete FSH and LH that act on gonads
• _ cells - secrete Prolactin that stimulates milk production

Answer 4

Major Cell Types in Anterior Pituitary

• Somatotropic cells - secrete GH
• Thryotropic cells - secrete TSH regulating thyroid gland secretion
• Corticotropic cells - secrete ACTH and MSH
  
  • ACTH stimulates adrenal cortex to secrete stress-related hormones and mediate metabolism
  • MSH stimulates melanocytes to produce melanin
• Gonadotropic cells - secrete FSH and LH that act on gonads
• Mammotropic cells - secrete Prolactin that stimulates milk production

Question 5

Cells of Pars Distalis (Anterior Pituitary)

• _ (lighter staining)
  
  • Somatotrophs - GH
  • Mammotrophs - Prolactin
• _ (darker staining)
  
  • Corticotrophs - ACTH
  • Thyrotrophs - TSH
  • Gonadotrophs - FSH/LH
• Chromotrophs - unknown function
• Sinusoidal (fenestrated) capillaries

Answer 5

Cells of Pars Distalis (Anterior Pituitary)

• Acidphils (lighter staining)
  
  • Somatotrophs - GH
  • Mammotrophs - Prolactin
• Basophils (darker staining)
  
  • Corticotrophs - ACTH
  • Thyrotrophs - TRH
  • Gonadotrophs - FSH/LH
• Chromotrophs - unknown function
• Sinusoidal (fenestrated) capillaries

Question 6

Pars Intermedia

• Between pars _ and pars _
• Rudimentary in adults and function unknown
• Small _ and colloid-filled follicles lined by cuboidal epithelium
• Frequently has cleft (remnant of lumen of _ pouch)

Answer 6

Pars Intermedia

• Between Pars Distalis and Pars Nervosa
• Rudimentary in adults and function unknown
• Small Basophils and colloid-filled follicles lined by cuboidal epithelium
• Frequently has cleft (remnant of lumen of Rathke’s pouch)

Question 7

Pars Nervosa

• Continues with median eminence of hypothalamus via _ _
• Does not manufacture hormones, rather stores and releases them from axon terminals
• Consists of:
  
  • Hypothalamic unmyelinated axons
    
    • _ bodies - expanded axonal nerve terminals storing ADH/Oxytocin
  • _ (glia-like) supporting the nerver fibers
  • _ capillaries

Answer 7

Pars Nervosa

• Continues with median eminence of hypothalamus via Infundibular Stalk
• Does not manufacture hormones, rather stores and releases them from axon terminals
• Consists of:
  
  • Hypothalamic unmyelinated axons
    
    • Herring bodies - expanded axonal nerve terminals storing ADH/Oxytocin
  • Pituicytes (glia-like) supporting the nerver fibers
  • Fenestrated capillaries

Question 8

Infundibulum

• Suspends pituitary gland from hypothalamus
• _ portion (infundibular stalk) - part connecting the pars _ and _ _ of hypothalamus
  
  • Consists of unmyelinated axons (nerve body in hypothalamus, terminals in pars nerovsa)
• _ portion - surrounding pars _ enveloping the infundibular stalk. May form a partial or total collar
  
  • Consists of numerous cuboidal cells arranged in cords

Answer 8

Infundibulum

• Suspends pituitary gland from hypothalamus
• Neural portion (infundibular stalk) - part of neurohypophysis connecting the Pars Nervosa and Median Eminence of hypothalamus
  
  • Consists of unmyelinated axons (nerve body in hypothalamus, terminals in pars nerovsa)
• Adenohypophysis portion - surrounding Pars Tuberalis enveloping the infundibular stalk. May form a partial or total collar
  
  • Consists of numerous cuboidal cells arranged in cords

Question 9

Blood Supply to Hypophysis:

Hypothalamo-Hypophyseal Portal System

Question 10

Posterior Pituitary Gland: Hypothalamo-Hypophyseal Tract

• _ - targets the kidney; regulates sodium and water retention
• _ - targets uterine smooth muscle and stimulates lactation; induces birth. May be involved in sexual arousal and pair and social bonding.

Answer 10

Posterior Pituitary Gland: Hypothalamo-Hypophyseal Tract

• ADH - targets the kidney; regulates sodium and water retention
• Oxytocin - targets uterine smooth muscle and stimulates lactation; induces birth. May be involved in sexual arousal and pair and social bonding.

Question 11

Pineal Gland

• Out pocketing of diencephalon’s roof of 3rd ventricle
• Flatten cone-shaped, 3-5 mm diameter
• Role in growth, development and _ rhythms
• Covered with pia mater
• Synthesizes _ and serotonin
• Consists of:
  
  • _
  • Neuroglia
  • Calcified granular material (brain sand)
    
    • Ca₃(PO₄)₂ crystals located intercellular spaces showing up beginning early childhood; important radiogenic marker (for midline brain; secreted by pinealocytes)

Answer 11

Pineal Gland

• Out pocketing of diencephalon’s roof of 3rd ventricle
• Flatten cone-shaped, 3-5 mm diameter
• Role in growth, development and Circadian rhythms
• Covered with pia mater
• Synthesizes Melatonin and serotonin
• Consists of:
  
  • Pinealocytes
  • Neuroglia
  • Calcified granular material (brain sand)
    
    • Ca₃(PO₄)₂ crystals located in intercellular spaces showing up beginning early childhood; important radiogenic marker (for midline brain; secreted by pinealocytes)

Question 12

Thyroid Anatomy and Blood Supply

• Butterfly-shaped, bi-lobed endocrine gland just below larynx and anterior to trachea
• Blood supply is from the _ _ vessels and _ _ vessels

Answer 12

Thyroid Gland and Blood Supply

• Butterfly-shaped, bi-lobed endocrine gland just below larynx and anterior to trachea
• Blood supply is from the superior thyroid vessels and inferior thyroid vessels

Question 13

Microscopic Anatomy of Thyroid

• Characterized by structures called _ consisting of a layer of _ cells (simple cuboidal to columnar epithelium) surrounding a fluid called _
• Colloid contains _, a storage form of the thyroid hormones, _ and _ (iodine-containing hormones)
• Only gland to store hormone outside the cell. Thyroid hormones control basal metabolism, O₂ usage, body temperature, etc.

Answer 13

Microscopic Anatomy of Thyroid

• Characterized by structures called follicles consisting of a layer of follicular cells (simple cuboidal to columnar epithelium) surrounding a fluid called colloid
• Colloid contains thyroglobulin, a storage form of the thyroid hormones, T3 and T4 (iodine-containing hormones)
• Only gland to store hormone outside the cell. Thyroid hormones control basal metabolism, O2usage, body temperature, etc.

Question 14

Parafollicular C Cells

• Lie just outside the follicles
• Secrete _ when blood levels of calcium are high
• Lowers circulating calcium levels by:
  
  • Stimulating secretion by kidneys
  • Decreasing the calcium-releasing activity of osteoclasts
  • Increasing osteogenesis by osteoblasts

Answer 14

Parafollicular C Cells

• Lie just outside the follicles
• Secrete Calcitonin when blood levels of calcium are high
• Lowers circulating calcium levels by:
  
  • Stimulating secretion by kidneys
  • Decreasing the calcium-releasing activity of osteoclasts
  • Increasing osteogenesis by osteoblasts

Question 15

Parathyroid Glands

• Small ovoid glands lying on the posterior surface of the thyroid gland that release _
  
  • Usually two pairs but can be more.
• Major importance in regulating serum _ and _ levels.
• Blood supply to the parathyroid glands
  is similar to the thyroid.

Answer 15

Parathyroid Glands

• Small ovoid glands lying on the posterior surface of the thyroid gland that release PTH
  
  • Usually two pairs but can be more.
• Major importance in regulating serum Calcium and Phosphate levels.
• Blood supply to the parathyroid glands
  is similar to the thyroid.

Question 16

Parathyroid Gland Microscopic Anatomy

• _ cells release parathyroid hormone (PTH)
  
  • Secretion occurs when the blood concentration of calcium falls below the normal range of 9.5-10.5 mg/dL
  • Secretion stops when the level of calcium returns to normal
• _ cells - function unknown

Answer 16

Parathyroid Gland Microscopic Anatomy

• Chief (Principle) Cells release parathyroid hormone (PTH)
  
  • Secretion occurs when the blood concentration of calcium falls below the normal range of 9.5-10.5 mg/dL
  • Secretion stops when the level of calcium returns to normal
• Oxyphil Cells - function unknown

Question 17

Adrenal Gland Microscopic Anatomy

• The gland is divided into an outer _ and an inner central core called the _

Answer 17

Adrenal Gland Microscopic Anatomy

• The gland is divided into an outer Adrenal Cortex and an inner central core called the Adrenal Medulla

Question 18

Adrenal Gland Cortex

Question 19

Adrenal Cortex

• Distinctive yellow color due to stored _ in its cells
• More than 25 different steroid hormones ( _ ) are secreted from the cortex; vital for survival
• Structurally and functionally 3 zones:
  
  • Zona _ ( _-corticoids) - influence sodium and potassium levels (salt)
    
    • _ – targets kidney function. Mostly secreted in response to low BP or blood volume; controlled by RAAS
  • Zona _ ( _-corticoids) - influence glucose metabolism and immune system; released under the control of _ from the anterior pituitary.
    
    • _ - deals with stress and mediates glucose metabolism and serves as negative feedback mechanism for the immune system (anti-inflammatory action)
  • Zona _ ( _ ) - influence secondary sex characteristics

Answer 19

Adrenal Cortex

• Distinctive yellow color due to stored Lipids in its cells
• More than 25 different steroid hormones (Corticosteroids) are secreted from the cortex; vital for survival
• Structurally and functionally 3 zones:
  
  • Zona Glomerulosa (Mineralcorticoids) - influence sodium and potassium levels (salt)
    
    • Aldosterone - targets kidney function. Mostly secreted in response to low BP or blood volume; controlled by RAAS
  • Zona Fasciculata (Glucocorticoids) - influence glucose metabolism and immune system; released under the control of ACTH from the anterior pituitary.
    
    • Cortisol - deals with stress and mediates glucose metabolism and serves as negative feedback mechanism for the immune system (anti-inflammatory action)
  • Zona Reticularis (Androgens) - influence secondary sex characteristics

Question 20

Adrenal Medulla

• Forms the inner core of each adrenal gland
• Primarily consists of clusters of large, spherical cells called _ cells (target of sympathetic neurons)
• When stimulated by the sympathetic division of the ANS, one population of cells secretes the hormone _ ( _ ) and a second population secretes the hormone _ ( _ )
• These hormones work with the sympathetic nervous system to prepare the body for an emergency or fight-or-flight situation

Answer 20

Adrenal Medulla

• Forms the inner core of each adrenal gland
• Primarily consists of clusters of large, spherical cells called Chromaffin Cells (target of sympathetic neurons)
• When stimulated by the sympathetic division of the ANS, one population of cells secretes the hormone Epinephrine (Adrenaline) and a second population secretes the hormone Norepinephrine (Noradrenaline)
• These hormones work with the sympathetic nervous system to prepare the body for an emergency or fight-or-flight situation

Question 21

Chromaffin Cells

• _ cells - smaller with granules less electron dense
• _ cells - larger with granules more electron dense

Answer 21

Chromaffin Cells

• Epinephrine Cells - smaller with granules less electron dense
• Norepinephrine Cells - larger with granules more electron dense

Question 22

Pancreas Histology​

• Exocrine portion makes up most of the gland; aids in digestion
• Exocrine cells are organized in structures called _ _
• Endocrine cells organized into clusters called _ _ or _ of _
  
  • Scattered amongst the exocrine cells

Answer 22

Pancreas Histology​

• Exocrine portion makes up most of the gland; aids in digestion
• Exocrine cells are organized in structures called Pancreatic Acini
• Endocrine cells organized into clusters called Pancreatic Islets or Islets of Langerhans
  
  • Scattered amongst the exocrine cells

Question 23

Endocrine Pancreas

• _ cells secrete _ when blood glucose levels drop; stimulates release of glucose from liver glycogen stores
• _ cells secrete _ when blood glucose levels are elevated and promotes glycogen storage in liver and entry into cells
• _ cells secrete _ slowingthe release of insulin and glucagon thereby controlling the rate of nutrient entry into the bloodstream and cells; stimulated by high levels of nutrients in the bloodstream
• _ cells secrete _ _ that inhibit the release of somatostatin

Answer 23

Endocrine Pancreas

• Alpha Cells secrete Glucagon when blood glucose levels drop; stimulates release of glucose from liver glycogen stores
• Beta Cells secrete Insulin when blood glucose levels are elevated and promotes glycogen storage in liver and entry into cells
• Delta cells secrete Somatostatin slowingthe release of insulin and glucagon thereby controlling the rate of nutrient entry into the bloodstream and cells; stimulated by high levels of nutrients in the bloodstream
• F Cells secrete Pancreatic Polypeptide that inhibit the release of somatostatin

Question 24

Pancreatic Blood Supply