9 - Histology of Endocrine Organs Flashcards by Staci Thomas

Both of these systems influence the physiologic functions of other organs, but differ by the methods used to communicate and accomplish their influence.

Endocrine System

Nervous System

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In the _________ system, it involves membrane depolarization and transmission of a signal from synapses. Communication is rapid but effects on target cells/organs are short-lived.

Nervous

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In the _________ system, it involves chemicals called hormones that are distributed throughout the body by the cardiovascular system. Communication is much slower but the effects on target cells/organs are of longer duration.

Endocrine

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T/F. Neurons do not secrete hormones.

False. Some neurons do secrete hormones.

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This type of hormonal release is controlled by monitoring levels of ions and nutrients in blood and body fluids. An example is the release of parathyroid hormone stimulated by low serum calcium levels.

Humoral Stimuli

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This type of hormonal release is stimulated by nerve signals. An example is the release of epinephrine from the adrenal gland in response to a signal from sympathetic nerve fibers.

Neuronal Stimuli

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This type of hormonal release is caused by a hormone being secreted into the bloodstream by another endocrine organ or cell. An example is the release of thyroid hormone stimulated by the release of the hormone, TSH, from the pituitary.

Hormonal Stimuli

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Endocrine glands are made of _________ cells, which lack a free surface (apical lumen). They are arranged as cords/follicles and some as isolated individual cells. They are derived from epithelia.

Epithelioid

***Only gland that has a lumen is thyroid gland

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Endocrine glands are well vascularized, and vessels often have _________ endothelium.

Fenestrated

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What are the direct targets of Hypothalamic hormones, and what are the hormones?

Anterior Pituitary – releasing and inhibiting factors that influence its secretion

Kidney and Uterus – releasing ADH and oxytocin (stored in posterior pituitary)

Adrenal Medulla – Hypothalamus oversees ANS, helps via Sympathetic innervation

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The hypothalamus releases hormones, collectively referred to as ________ hormones, that stimulate or inhibit release of other hormones from the anterior pituitary.

Tropic

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The hypothalamus works indirectly by stimulating secretion of hormones by the anterior pituitary gland. Where do the hormones from the anterior pituitary go to?

Thyroid gland
Adrenal cortex
Mammary gland
Gonads (testes or ovaries)
Bone and other organs

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These cells from the anterior pituitary secrete TSH, which regulates thyroid gland secretion.

Thyrotropic cells

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These cells from the anterior pituitary secrete Prolactin, which stimulates milk production.

Mammotropic cells

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These cells from the anterior pituitary secrete ACTH and MSH.

Corticotropic cells

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These cells from the anterior pituitary secrete GH.

Somatotropic cells

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These cells from the anterior pituitary secrete FSH and LH, which act on the gonads.

Gonadotropic cells

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In the origin of the pituitary, ectodermal placode leading to _______ _______ is seen by 3 weeks. This loses it connection with the outside and is near final location by 8 weeks. It joins the diverticulum from the developing _________ of the neural tube.

Rathke’s Pouch

Diencephalon

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In the development of the pituitary, the __________ forms the posterior pituitary and the infundibular stalk. _______ _______ forms the rest of the pituitary.

Infundibulum

Rathke’s Pouch

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In the development of the pituitary, at what weeks do ACTH, GH, TSH and LH, and FSH start being produced?

ACTH – 7 weeks
GH – 8-9 weeks
TSH and LH – 12 weeks
FSH – 13 weeks

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The anterior pituitary constitutes ______ percent of the gland. It is comprised of glandular epithelial cells controlled by _________ released from the hypothalamus.

Neurohormones

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The posterior pituitary is comprised of axons from the __________ and support cells. The axons carry ______ and _______ for storage and release in the posterior pituitary.

Hypothalamus
ADH
Oxytocin

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What are the parts of the anterior pituitary (adenohypophysis)?

Pars tuberalis
Pars intermedia
Pars distalis

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What are the parts of the posterior pituitary (neurohypophysis)?

Infundibular stalk

Pars nervosa

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This is small and in between the anterior and posterior pituitary. It is a remnant of the lumen of Rathke's pouch.

Cyst Intermedia

This hormone stimulates the adrenal cortex to secrete stress-related hormones and mediate metabolism.

ACTH

This hormone stimulates melanocytes to produce melanin.

MSH

What are the cells of the Pars Distalis (in anterior pituitary)?

Acidphils Basophils Chromophobes Sinusoidal (fenestra) capillaries

What are the types of acidphil cells in the anterior pituitary?

Somatotrophs -- secrete GH | Mammotrophs -- secrete Prolactin

What are the types of basophil cells in the anterior pituitary?

Corticotrophs -- secrete ACTH Thyrotrophs -- secrete TSH Gonadotrophs -- secrete FSH/LH

This portion of the pituitary lies between Pars Distalis and Pars Nervosa. It is rudimentary in adults, and its function is unknown.

Pars Intermedia

Pars Intermedia contains small basophils and colloid-filled follicles lined by _________ epithelium. It frequently contains the _______ ______, which is remnant of lumen of Rathke's pouch.

Cuboidal | Cyst Intermedia

This portion of the pituitary is continuous with the median eminence of the hypothalamus via the infundibular stalk. It does NOT manufacture hormones, rather it stores and releases them from axon terminals.

Pars Nervosa

The Pars Nervosa consists of hypothalamic unmyelinated axons called _______ _______, which are expanded axonal nerve terminals storing ADH and Oxytocin.

Herring bodies

The Pars Nervosa contain _________, which are glia-like and support the nerve fibers. It also has fenestrated capillaries.

Pituicytes

Hypothalamic hormones are released into special blood vessels, called the _________ ________ _________, controls the release of anterior pituitary hormones.

Hypophyseal Portal System

What does a portal system consist of?

A portal system is two capillary plexuses (beds) connected by veins.

In the Hypophyseal Portal System, the ______ ______ artery is connected to the Primary Capillary Plexus. This plexus is connected to the Secondary Capillary Plexus via the _______ ______ veins.

Superior Hypophyseal A. | Hypophyseal Portal Vs.

Explain the steps of hormone release from the anterior pituitary involving the Hypophyseal Portal System.

1) When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the Primary Capillary Plexus. 2) Hypothalamic hormones travels through the Hypophyseal Portal Vs. to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. 3) In response to releasing hormones, the anterior pituitary secretes hormones into the Secondary Capillary Plexus. This in turn empties into the general circulation.

The posterior pituitary gland releases hormones via the ________ ________ tract.

Hypothalamo-Hypophyseal

This hormone from the posterior pituitary targets the kidney. It regulates sodium and water retention.

Antidiuretic Hormone (ADH)

This hormone from the posterior pituitary targets uterine smooth muscle and stimulates lactation, as well as induces birth. It may be involved in sexual arousal and pair and social bonding.

Oxytocin

Explain the pathway for hormones to the posterior pituitary in the Hypothalamo-Hypophyseal tract.

1) Hypothalamic neurons synthesize Oxytocin or ADH. 2) Oxytocin and ADH are transported down the axons of the Hypothalamo-Hypophyseal tract to the posterior pituitary. 3) Oxytocin and ADH are stored in neurosecretory bodies in the posterior pituitary. 4) When associated hypothalamic neurons fire, nerve impulses arriving at the neurosecretory bodies cause Oxytocin or ADH to be released into the blood.

This is an out-pocketing of the diencephalon's roof of the 3rd ventricle. It has a flattened cone-shape and is 3-mm in diameter. It is covered with Pia Mater.

Pineal Gland

The Pineal Gland has a role in growth, development, and circadian rhythms. It synthesizes ________ and _______.

Melatonin | Serotonin

What does the Pineal Gland consist of?

Pinealocytes Neuroglia Calcified granular material (brain sand)

The calcified granular material (brain sand) in the Pineal Gland is composed of ________ ________ crystals located in intercellular spaces that show up at the beginning of early childhood. It is an important radiogenic marker (for midline brain). It is secreted by _________.

Calcium Phosphate | Pinealocytes

This gland is characterized by structures called follicles, consisting of a layer of follicular cells (simple cuboidal to columnar epithelium) surrounding a fluid called colloid.

Thyroid

In the Thyroid, colloid contains _________, a storage form of the thyroid hormones T3 and T4 (iodine-containing hormones).

Thyroglobulin

This gland is the only one to store hormones outside of its cells.

Thyroid ***Inside the follicular lumen as colloid!

________ hormones control basal metabolism, oxygen usage, body temperature, etc.

Thyroid

Thyroglobulin is synthesized in the rER, glycosylated in the Golgi, and secreted by exocytosis into the lumen of the follicle, called ________.

Colloid

Thyroid hormone is iodinated at the apical surface, forming ______ and ______ that is bound to Thyroglobulin.

T3 | T4

______ stimulates internalization of Thyroglobulin via endocytosis where it is degraded, freeing T3 and T4.

TSH

T3 and T4 is released from the (APICAL/BASAL) surface of the follicle cells into the circulation.

Basal

These cells lie just outside the follicles in the Thyroid, and they secrete calcitonin when blood levels of calcium are HIGH.

Parafollicular C cells

How does calcitonin (from Parafollicular C cells) work to lower circulating calcium levels?

-- Stimulate secretion of calcium by kidneys (pee it out) -- Decreasing the calcium-releasing activity of osteoclasts -- Increasing osteogenesis by osteoblasts (use calcium to make bone)

This thyroid pathology is due to abnormal antibodies stimulating TSH receptors, causing over-secretion of T3 and T4. Symptoms include elevated metabolism, sweating, rapid heart rate, weight loss, and eyeballs may protrude. Can be treated with a thyroidectomy or anti-thyroid drugs.

Grave's disease

This thyroid pathology is due to insufficient T3 and T4 production. It is often an autoimmune disease-causing follicle cell death. Symptoms include low metabolic rate, weight gain, lethargy, chillness, edema, and being mentally sluggish. Can be treated with synthetic T3/T4.

Hypothyroidism

This is a thyroid enlargement most commonly due to iodine deficiency. Follicle cells keep producing Thyroglobulin but cannot iodinate it to make TH (T3 and T4).

Goiters ***More prevalent in areas of iodine deficiency, like 3rd world countries.

These are small ovoid glands lying on the posterior surface of the thyroid gland that release PTH. There are usually two pairs but can be more.

Parathyroid Glands

Parathyroid glands have a major importance in regulating serum ________ and ________ levels.

Calcium | Phosphate

These cells in the Parathyroid gland release PTH. The secretion of PTH occurs when the blood concentration of calcium falls below the normal range (9.5-10.5 mg/dL). Secretion stops when levels return to normal.

Chief (Principle) cells

These cells are also in the Parathyroid gland, but their function is unknown.

Oxyphil cells

When blood calcium levels drop below 9.5 mg/dL, then the parathyroid releases PTH into the bloodstream. What does the release of PTH cause to happen?

-- Stimulates osteoclasts to resorb bone and release its calcium stores -- Increase calcium retention by kidneys -- Stimulates kidney to convert an inactive form of Vitamin D to calcitriol (active Vitamin D), because calcitriol increases calcium absorption by the intestines ***Basically the exact opposite of Calcitonin (from Parafollicular C cells in Thyroid)

How is the adrenal gland divided?

Adrenal Cortex -- Outside Adrenal Medulla -- Inside ***Capsule lies outside the cortex, but it has no functions

What are the subdivisions of the Adrenal Cortex?

Zona Glomerulosa Zona Fasciculata Zona Reticularis

What is secreted from the Zona Glomerulosa?

Aldosterone

What is secreted from the Zona Fasciculata?

Cortisol (main hormone) | Androgens (a little bit)

What is secreted from the Zona Reticularis?

Androgens (main hormone) | Cortisol (a little bit)

This portion of the Adrenal Gland has a distinctive yellow color due to stored lips in its cells. It also has more than 25 different steroid hormones (corticosteroids) that it secretes, which are vital for survival.

Adrenal Cortex

The Zona Glomerulosa contains mineralocorticoids, specifically _________, which influences sodium and potassium levels.

Aldosterone

Aldosterone targets kidney function and is mostly secreted in response to low ________ _______ or ________ _______. It is controlled by the renin-angiotensin system.

Blood pressure | Blood volume

The Zona Fasciculata contains glucocorticoids, specifically ________, which influences glucose metabolism and the immune system.

Cortisol

Cortisol is released under the control of ________ from the anterior pituitary.

ACTH

Cortisol deals with stress and mediates glucose metabolism and serves as negative feedback mechanism for the immune system giving an __________ action.

Anti-inflammatory

These hormones influence secondary sex characteristics, and are primarily secreted by the Zona Reticularis.

Androgens

The Adrenal Medulla forms the inner core of each Adrenal gland. It primarily consists of clusters of large, spherical cells called _________ cells which are the target of sympathetic neurons.

Chromaffin

In the Adrenal Medulla, when stimulated by the sympathetic division of the ANS, one population of cells secretes the hormone _________ and a second population secretes the hormone _________.

Epinephrine (Adrenaline) | Norepinephrine (Noradrenaline)

This type of Chromaffin cell is smaller with granules, and less electron dense (appears lighter).

Epinephrine cells

This type of Chromaffin cell is larger with granules, and more electron dense (appears darker).

Norepinephrine

This type of adrenal gland syndrome is a hyposecretory disorder usually in both glucocorticoids (cortisol) and mineralocorticoids (aldosterone). Blood glucose and sodium levels drop, there is severe dehydration and low BP along with fatigue and loss of appetite. It is usually caused by an autoimmune disease or due to inherited metabolic disease leading to deficiencies in hormone-producing enzymes.

Addison's Disease

This type of adrenal gland syndrome is due to hypersecretion of glucocorticoids (cortisol) because of either an ACTH-secreting pituitary tumor or a tumor in the adrenal cortex. It is characterized by high serum glucose levels, protein loss in muscles, muscle weakness, and lethargy. Rare in humans.

Cushing's Syndrome

The following symptoms describe what disease? - - Swollen face (Moon face) - - Buffalo hump - - High glucose levels - - Weight gain - - Sweating - - Thinning skin - - Muscle weakness - - Lethargy - - Depression of immune and inflammatory responses

Cushing's Syndrome

For the Pancreas, it has an endocrine and exocrine portion. The exocrine portions makes up most of the gland and it aids in _________.

Digestion

Exocrine cells of the Pancreas are organized in structures called ________ ________. Endocrine cells are organized into clusters called ________ ________ or ________ _______ ________, which are scattered among the exocrine cells.

Pancreatic Acini Pancreatic Islets Islets of Langerhans

In the endocrine portion of the Pancreas (Islets of Langerhans), what cells are present and what hormones do they secrete?

Alpha cells -- Glucagon Beta cells -- Insulin Delta cells -- Somatostatin F cells -- Pancreatic Polypeptide

When blood glucose levels drop, ________ is released from Alpha cells in the Pancreas to stimulate the release of glucose from liver glycogen stores.

Glucagon

When blood glucose levels are elevated, ________ is released from Beta cells in the Pancreas to promote glycogen storage in the liver and entry into cells.

Insulin

In the Pancreas, Delta cells release __________ to slow the release of insulin and glucagon, thereby controlling the rate of nutrient entry into the bloodstream and cells. These cells are stimulated by high levels of nutrients in the bloodstream.

Somatostatin

In the Pancreas, F-cells release ________ ________ which inhibit the release of somatostatin.

Pancreatic Polypeptide

Each Islet of Langerhans is supplied by afferent arterioles, forming a network of capillaries lined by fenestrated endothelial cells. This network is called the ________ _______ _______.

Insuloacinar Portal System

Capillaries leaving the Islet of Langerhans supply blood to the _______ ______ surrounding the islet. This vascular system enables a local action on the exocrine pancreas of hormones produced in the islet.

Pancreatic Acini ***Remember, Pancreatic Acini are the exocrine part of the Pancreas

Pancreatic Acini can also receive blood via an independent arterial system called the _______ _______ _______.

Acinar Vascular System