Endocrine PDF Flashcards
(248 cards)
1
Q
How is the endocrine system divided?
A
The endocrine system is divided into organs with a primary endocrine function and those with other primary functions but also secondary endocrine function.
2
Q
What are some of the primary endocrine organs considered in these notes?
A
Primary endocrine organs include the pineal gland, hypothalamus, pituitary, thyroid, parathyroids, pancreas, adrenals, and gonads (ovaries and testes).
3
Q
What aspect of endocrine glands is considered in these notes, contrasting with physiology and histology?
A
These notes focus on the gross anatomy of primary endocrine organs, whereas it is important to revise the physiology (including control mechanisms and end actions) and histology separately.
4
Q
What hormone does the Heart produce in response to increased blood volume or pressure stretching the atrial wall?
A
The Heart produces and secretes the peptide hormone atrial natriuretic peptide (ANP).
5
Q
What are the actions of Atrial Natriuretic Peptide (ANP)?
A
ANP acts on the kidneys to reduce sodium reabsorption and hence water resorption, reducing blood volume. It also inhibits renin secretion and the renin-angiotensin-aldosterone system (RAAS), and causes vasodilation, thus aiding in decreasing blood pressure, blood volume, and blood sodium levels.
6
Q
Where are the endocrine cells of the Gastrointestinal (GI) tract located?
A
The endocrine cells of the GI tract are in the mucosa of the stomach and small intestine.
7
Q
What hormone is secreted by G cells in the stomach in response to stomach distention, and what does it stimulate?
A
Gastrin is secreted by G cells and stimulates the release of hydrochloric acid.
8
Q
Where is Ghrelin produced, and how do its circulating levels change with fasting or eating?
A
Ghrelin is produced in oxyntic glands of the stomach by P/D1 cells. Ghrelin levels increase during periods of fasting or negative energy balance and are low after eating or with hyperglycemia and obesity.
9
Q
What is the central role of Ghrelin?
A
Ghrelin plays a central role in the neurohormonal regulation of food intake and energy homeostasis.
10
Q
What does Ghrelin stimulate and produce?
A
Ghrelin stimulates the secretion of growth hormone, increases food intake, and produces weight gain.
11
Q
What hormone is secreted by the small intestine when acidic chyme moves from the stomach, and what are its actions?
A
Secretin is secreted by the small intestine. It stimulates the release of bicarbonate from the pancreas and inhibits further secretion of hydrochloric acid by the stomach.
12
Q
What hormone is released from the small intestine that promotes the secretion of pancreatic digestive enzymes and bile from the gallbladder?
A
Cholecystokinin (CCK), also called Pancreozymin, is released from the small intestine.
13
Q
How do other hormones produced by intestinal cells aid in glucose metabolism?
A
They aid in glucose metabolism by stimulating pancreatic beta cells to secrete insulin, reducing glucagon secretion from alpha cells, or enhancing cellular sensitivity to insulin.
14
Q
How do the Kidneys participate in endocrine pathways when blood flow decreases?
A
Decreased blood flow stimulates the release of the enzyme renin, triggering the renin-angiotensin-aldosterone (RAAS) system, which stimulates the reabsorption of sodium and water, increasing blood pressure.
15
Q
How do the Kidneys regulate blood calcium levels?
A
The kidneys produce calcitriol from vitamin D3, which is released in response to parathyroid hormone (PTH) secretion.
16
Q
What hormone do the Kidneys produce in response to low oxygen levels, and what does it stimulate?
A
The kidneys produce erythropoietin (EPO) in response to low oxygen levels. EPO stimulates the production of red blood cells (erythrocytes) in the bone marrow, increasing oxygen delivery.
17
Q
What hormone does the Skeleton produce in response to increased blood levels of vitamin D3 or phosphate, and what does it trigger in the kidneys?
A
The skeleton produces Fibroblast growth factor 23 (FGF23). It triggers the kidneys to inhibit calcitriol formation from vitamin D3 and to increase phosphorus excretion.
18
Q
What hormone is produced by osteoblasts, and what are its actions?
A
Osteocalcin is produced by osteoblasts. It stimulates pancreatic beta cells to increase insulin production and acts on peripheral tissues to increase their sensitivity to insulin and their glucose utilization.
19
Q
What are some hormones produced and secreted by Adipose Tissue?
A
Adipose tissue produces and secretes hormones involved in lipid metabolism and storage, such as leptin and adiponectin.
20
Q
How does Leptin function?
A
Leptin is an adipose protein that circulates in amounts proportional to body fat. It is released in response to food consumption and acts by binding to brain neurons involved in energy intake and expenditure, producing a feeling of satiety and reducing appetite. It also appears to trigger the sympathetic nervous system to regulate bone metabolism, increasing cortical bone deposition.
21
Q
What is Adiponectin, and how are its levels related to obesity and weight loss?
A
Adiponectin is a hormone synthesized by adipose cells that reduces cellular insulin resistance. Its levels are lower in people who are obese and rise following weight loss.
22
Q
How does the Skin function as an endocrine organ?
A
The skin functions in the production of the inactive form of vitamin D3, cholecalciferol, when cholesterol in the epidermis is exposed to ultraviolet radiation.
23
Q
What happens to cholecalciferol after it is produced in the skin?
A
Cholecalciferol enters the blood, is converted to an intermediate in the liver, and is further converted to calcitriol (the active form of vitamin D3) in the kidneys.
24
Q
What is the importance of Vitamin D (Calcitriol)?
A
Vitamin D is important in various physiological processes, including intestinal calcium absorption and immune system function.
25
What is the primary endocrine function of the Thymus?
The Thymus produces a group of hormones called thymosins that contribute to the development and differentiation of T lymphocytes.
26
How does the size and activity of the Thymus change with age?
The Thymus is larger and more active during infancy and early childhood and begins to atrophy as we age.
27
What are some important hormones or hormone precursors secreted by the Liver?
The liver is responsible for secreting insulin-like growth factor-1 (somatomedin), angiotensinogen, thrombopoetin, and hepcidin.
28
What is the function of Insulin-like growth factor-1?
Insulin-like growth factor-1 is the immediate stimulus for growth in the body, especially of the bones.
29
What is the function of Angiotensinogen secreted by the liver?
Angiotensinogen is the precursor to angiotensin I, which increases blood pressure via conversion to angiotensin II by ACE.
30
What is the function of Thrombopoetin secreted by the liver?
Thrombopoetin stimulates the production of the blood's platelets.
31
What is the function of Hepcidins secreted by the liver?
Hepcidins block the release of iron from cells in the body, helping to regulate iron homeostasis in body fluids.
32
Where is the Pineal Gland located?
The Pineal Gland develops from the roof of the diencephalon and is located behind the third ventricle in the midline between the two cerebral hemispheres.
33
What are the key anatomical relations of the Pineal Gland?
It is bounded by the splenium of the corpus callosum and tela choroidea dorsally, the midbrain tectum ventrally, the posterior aspect of the third ventricle rostrally, and the cerebellar vermis caudally.
34
What is the blood supply to the Pineal Gland?
The blood supply is via the posterior choroidal arteries, which arise from the posterior cerebral artery.
35
What hormone does the Pineal Gland produce, and what does it modulate?
The pineal gland produces melatonin, a serotonin derived hormone which modulates sleep patterns in both circadian and seasonal cycles.
36
How do melatonin levels change throughout the day?
The level of melatonin rises during darkness and decreases during the day.
37
How is cyclical pineal behaviour thought to be governed?
It is thought that the intrinsic rhythmicity of an endogenous circadian oscillator in the suprachiasmatic nucleus of the hypothalamus governs cyclical pineal behaviour.
38
How is the Pineal Gland innervated?
The pineal gland is richly innervated with sympathetic noradrenergic input from a pathway originating in the retina, coursing through the suprachiasmatic nucleus of the hypothalamus and the superior cervical ganglion.
39
What are the general categories of tumours in the pineal region?
Tumours of the pineal region can be divided into germ cell and non–germ cell derivatives.
40
What are some clinical symptoms of pineal region tumours?
Clinical symptoms include symptoms of a space occupying lesion such as headache, nausea, and vomiting. They can also cause an inability to look upwards (Parinaud Syndrome) due to pressure on the superior colliculus or obstruct the cerebral aqueduct leading to hydrocephalus.
41
What condition is sometimes associated with abnormal melatonin secretion?
There is some evidence that melatonin secretion may be abnormal in Seasonal Affective Disorder (SAD).
42
How does the pineal gland modify the activity of other endocrine organs?
The pineal modifies the activity of the adenohypophysis, neurohypophysis, endocrine pancreas, parathyroids, suprarenal cortex, suprarenal medulla and gonads, with effects largely inhibitory.
43
How are hormones secreted by pinealocytes circulated to target cells?
Pineal secretions circulate to their target cells by the cerebrospinal fluid or the blood stream.
44
What are corpora arenacea, and where do they accumulate?
Corpora arenacea ('brain sand') are calcium deposits that accumulate in the pineal extracellular matrix from the second decade.
45
How can pineal gland calcifications be clinically useful?
Calcification can provide a useful indicator of a space-occupying lesion if the gland is significantly displaced from the midline.
46
Where is the Hypothalamus located and what is its structure?
The hypothalamus sits below the thalamus and encapsulates the ventral portion of the third ventricle. It is a small cone-shaped structure that projects downward, ending in the pituitary (infundibular) stalk.
47
What is the source of the hypophyseal arteries that supply the hypothalamus and pituitary?
The hypophyseal arteries originate from the internal carotid artery.
48
What is the function of the portal system supplied by the hypophyseal arteries?
They supply portal systems connecting the hypothalamus with the anterior pituitary, allowing transport and exchange of hormones between them.
49
What are some of the factors (hormones) secreted by neurosecretory neurons in the hypothalamus?
Hypothalamic neurosecretory neurons secrete thyrotropin-releasing hormone (TRH), growth hormone-releasing hormone (GHRH), growth hormone-inhibiting hormone (GHIH), gonadotropin-releasing hormone (GnRH), corticotropin-releasing hormone (CRH), oxytocin, and antidiuretic hormone (ADH).
50
What are some potential causes of Hypothalamic disorders?
Hypothalamic disorders may be caused by damage resulting from malnutrition, genetic disorders, radiation, surgery, head trauma, lesion, tumour, or other physical injury.
51
Why is it often difficult to differentiate between diseases of the hypothalamus and the pituitary?
The endocrine abnormalities are often similar because the hypothalamus regulates pituitary function.
52
What combination of symptoms is usually seen in hypothalamic damage?
As the hypothalamus regulates both endocrine and autonomic function, there is usually a combination of endocrine and neurological disturbance, including abnormal behaviour, eating disorders, and thermoregulation.
53
What anatomical landmarks are used to delineate the lateral and medial zones of the hypothalamus?
The lateral and medial zones are delineated by a line running between the fornix and the mammillothalamic tract.
54
How is the medial zone of the hypothalamus traditionally divided?
The medial zone is traditionally divided into the supraoptic, tuberal, and mammillary regions, named based on location and function/structures they contain.
55
What are examples of nuclei found in the supraoptic region of the medial hypothalamus?
The supraoptic region contains the supraoptic and paraventricular nuclei.
56
Where is the periventricular zone of the hypothalamus located?
The periventricular zone runs alongside the third ventricle.
57
Where is the preoptic area located, and what functions is it involved in?
The preoptic area is at the rostral aspect of the hypothalamus. It is involved in regulating body temperature, reproductive behaviours, and other autonomic functions.
58
Where is the Pituitary Gland located?
The pituitary gland is suspended from the underside of the brain by the pituitary stalk (infundibulum) and sits within a small depression in the sphenoid bone called the sella turcica.
59
What structure covers the superior aspect of the pituitary gland?
The superior aspect of the pituitary is covered by a fold of dura, the diaphragma sellae.
60
What important structure is in close proximity to the inferior surface of the brain near the pituitary?
The optic chiasm is in close proximity to the pituitary.
61
What venous sinuses and cranial nerves are adjacent to the lateral aspects of the pituitary?
The lateral aspects are adjacent to the cavernous sinuses, containing cranial nerves III (oculomotor), IV (trochlear), VI (abducens), V1 (ophthalmic branch of trigeminal nerve), and V2 (maxillary branch of trigeminal nerve).
62
What are the two functionally distinct parts of the pituitary gland?
The pituitary is composed of the adenohypophysis (anterior pituitary) and neurohypophysis (posterior pituitary).
63
What allows hypothalamic hormones to reach the adenohypophysis?
The hypothalamo-hypophysial portal venous system allows delivery of hypothalamic hormones to the adenohypophysis.
64
How does the neurohypophysis secrete hormones?
The neurohypophysis secretes hormones directly into the venous draining system of the pituitary.
65
What percentage of the pituitary gland does the adenohypophysis constitute?
The adenohypophysis constitutes roughly 80% of the pituitary gland.
66
What does the amo-hypophysial portal venous system allow?
It allows delivery of hypothalamic hormones to the adenohypophysis.
67
Where does the adenohypophysis receive most of its blood supply from?
It receives most of its blood supply from the paired superior hypophyseal arteries, which arise from the medial aspect of the internal carotid artery.
68
How is the release of adenohypophysis hormones mediated?
The release is mediated by hypothalamic neurohormones secreted from the median eminence and reaching the adenohypophysis via a portal venous system.
69
What hormones are produced in the adenohypophysis (anterior pituitary)?
Hormones produced include adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), growth hormone (GH), luteinizing hormone (LH), prolactin (PRL), and thyroid-stimulating hormone (TSH).
70
What supplies blood to the neurohypophysis (posterior pituitary)?
The neurohypophysis is supplied by the inferior hypophyseal arteries, terminal branches of the meningohypophyseal trunk from the cavernous portion of the internal carotid artery.
71
Does the neurohypophysis synthesize hormones?
No, the neurohypophysis is not glandular and does not synthesize hormones.
72
What is the function of the neurohypophysis regarding hormones?
It is a site where axons project from hypothalamic neuronal cell bodies that produce hormones, which undergo axonal transport and are released directly into the systemic vasculature.
73
What hormones are stored and released by the neurohypophysis (posterior pituitary)?
The neurohypophysis stores and releases Anti-diuretic hormone (ADH) and Oxytocin.
74
What is the function of Anti-diuretic hormone (ADH)?
ADH prompts the kidneys to increase water absorption in the blood.
75
What is the function of Oxytocin?
Oxytocin is involved in processes such as contracting the uterus during childbirth and stimulating breast milk secretion.
76
What can pituitary tumours lead to?
Pituitary tumours may lead to over or under production of pituitary hormones, resulting in specific diseases depending on the affected hormone(s).
77
How can pituitary enlargement affect vision?
Enlargement of the pituitary by tumour can cause compression of the optic chiasm leading to visual field defects.
78
What surgical approach is sometimes used to remove pituitary tumours?
Sometimes tumours may be removed surgically through the nose and sphenoid air sinus (trans-sphenoidal hypophysectomy).
79
What can cause acute pituitary infarction and hypopituitarism?
Hypotension after massive haemorrhage can lead to acute pituitary infarction and hypopituitarism.
80
What is Sheehan's syndrome?
Sheehan's syndrome is hypopituitarism caused by ischaemic necrosis due to blood loss and hypovolemic shock during or after childbirth.
81
What structure forming the diaphragma sellae has a central aperture?
The dura mater forming the circular diaphragma sellae has a central aperture for the infundibulum.
82
What is the embryological origin of the neurohypophysis?
The neurohypophysis is a diencephalic downgrowth connected with the hypothalamus.
83
What is the embryological origin of the adenohypophysis?
Embryologically the adenohypophysis is an ectodermal derivative of the stomatodeum.
84
What structures are included in the term 'neurohypophysis'?
The term neurohypophysis includes the median eminence, infundibular stem, and neural lobe or pars posterior.
85
What structures constitute the main mass of the adenohypophysis?
The main mass of the adenohypophysis may be divided into the pars anterior (also called pars distalis) and the pars intermedia.
86
What is the pars tuberalis?
The pars tuberalis is a component of the adenohypophysis that surrounds the infundibular stem.
87
Where is the Thyroid Gland located?
The thyroid gland is a highly vascular gland lying anteriorly in the neck, inferior to the thyroid cartilage, wrapping around the cricoid cartilage and superior tracheal rings. It extends from C5 down to T1.
88
What muscles lie behind the thyroid gland?
It lies behind the sternohyoid and sternothyroid muscles.
89
What are the main anatomical components of the Thyroid Gland?
The gland has 2 elongated lateral lobes connected by an isthmus.
90
Where does the isthmus of the thyroid typically lie?
The isthmus overlies the second to fourth tracheal rings.
91
What is the pyramidal lobe of the thyroid?
The pyramidal lobe is an occasional lobe that generally branches off the isthmus and ascends superiorly to the hyoid bone.
92
What is the embryological remnant associated with the pyramidal lobe and its presence?
The pyramidal lobe's presence is due to the thyroglossal duct, a passage via which the thyroid gland descends during embryology.
93
What can form if portions of the thyroglossal duct remain?
Portions of the duct may remain and form thyroglossal duct cysts.
94
What is lingual thyroid?
Lingual thyroid is a variant where thyroid tissue is found at the base of the tongue, where the gland initially develops during foetal life at the foramen caecum.
95
What attaches the thyroid capsule to the cricoid and thyroid cartilages?
The capsule is continuous with the pre-tracheal fascia and attaches the gland via a thickening called the posterior suspensory ligament of thyroid gland (Berry's ligament).
96
What are important structures located posterior to the thyroid gland?
Important structures posterior to the thyroid gland include the carotid sheath, containing the common carotid artery, the interior jugular vein, the vagus nerve, and deep lymph nodes of the neck.
97
What are the two main arteries supplying blood to the Thyroid Gland?
Blood supply is achieved by the superior and inferior thyroid arteries.
98
What is the origin of the superior thyroid artery?
The superior thyroid artery is the first branch of the external carotid artery.
99
What is the origin of the inferior thyroid artery?
The inferior thyroid artery arises from the thyrocervical trunk (a branch of the subclavian artery).
100
What important nerves are intimately associated with the inferior thyroid artery and its branches, and what is the risk during thyroid surgery?
The recurrent laryngeal nerves from the vagus nerves are intimately associated. They are at risk in thyroid surgery, and damage can lead to a hoarse voice (unilateral damage) or difficulty breathing (bilateral damage).
101
Is there ever an additional artery supplying the thyroid?
Yes, in around 10% of people there is an additional artery present called the thyroid ima artery.
102
What is the origin of the thyroid ima artery?
The thyroid ima artery comes from the brachiocephalic trunk of the arch of aorta.
103
What is the venous drainage of the Thyroid Gland?
Venous drainage is by the superior, middle, and inferior thyroid veins, which form a venous plexus. The superior and middle veins drain into the internal jugular veins, and the inferior drains into the brachiocephalic vein.
104
What is the lymphatic drainage of the Thyroid Gland?
Lymphatic drainage frequently passes the prelaryngeal lymph nodes, and the pretracheal and paratracheal lymph nodes.
105
How is glandular secretion of the thyroid controlled?
Glandular secretion is primarily under hormonal control of TSH from the pituitary.
106
What is the principal innervation of the Thyroid Gland?
Principal innervation is from the parasympathetic fibres of the vagus nerves, and sympathetic fibres from the superior, middle, and inferior ganglia of the sympathetic trunk.
107
What is the postulated effect of the sympathetic and parasympathetic nerves on the thyroid gland?
Most of their effect is postulated to be on blood vessels, influencing the perfusion rates of the glands.
108
How can the Parathyroid Glands be distinguished from the thyroid gland or lymph nodes in life?
Parathyroid glands have a distinct, encapsulated, smooth surface and are typically light brown to tan in colour, differing from the thyroid's lobular surface or lymph nodes' pitted appearance.
109
Where are the Parathyroid Glands located?
They are located on the posterior aspect of the lateral lobes of the thyroid, external to the gland itself but within its sheath.
110
What is the typical number of Parathyroid Glands people have?
The majority of people have four parathyroid glands, although variation in number is common.
111
From which embryological structures are the superior parathyroid glands derived?
The superior parathyroid glands are embryologically derived from the fourth pharyngeal pouch.
112
Where are the superior parathyroid glands typically located?
They are located approximately 1cm superior to the entry of the inferior thyroid arteries into the thyroid gland, at the level of the inferior border of the cricoid cartilage.
113
From which embryological structures are the inferior parathyroid glands derived?
The inferior parathyroid glands are embryologically derived from the third pharyngeal pouch.
114
Where are the inferior parathyroid glands usually found, and what is a possible variation in location?
The inferior parathyroid glands are usually found near the inferior poles of the thyroid gland. Their position can be variable, and they can sometimes be found as far inferiorly as the superior mediastinum.
115
What arteries supply blood to the Parathyroid Glands?
The inferior thyroid arteries primarily supply the parathyroid glands.
116
What provides collateral circulation to the Parathyroid Glands?
Collateral circulation is delivered by the superior thyroid arteries, thyroid ima artery, and laryngeal, tracheal and oesophageal arteries.
117
Where do the parathyroid veins drain?
The parathyroid veins drain into the thyroid plexus of veins.
118
What is the nerve supply to the Parathyroid Glands?
The parathyroid glands have an extensive supply of nerves from the cervical sympathetic ganglia.
119
Are the nerves supplying the parathyroid glands secretomotor or vasomotor?
These nerves are vasomotor, not secretomotor. Endocrine secretion of parathyroid hormone is controlled hormonally.
120
Where do the lymphatic vessels of the Parathyroid Glands drain?
The lymphatic vessels drain along with those of the thyroid gland.
121
What is the most common disorder of the parathyroids?
The most common disorder is excessive production of parathyroid hormone (hyperparathyroidism).
122
What is Primary hyperparathyroidism caused by?
Primary hyperparathyroidism is caused by enlargement of one or more of the parathyroid glands, leading to overproduction of the hormone.
123
What is a result of primary hyperparathyroidism in terms of blood calcium levels?
Primary hyperparathyroidism results in high levels of calcium in the blood (hypercalcemia).
124
What are some common symptoms of primary hyperparathyroidism?
Common symptoms include chronic fatigue, body aches, difficulty sleeping, bone pain, memory loss, poor concentration, depression, and headaches.
125
What other conditions can parathyroid disease frequently lead to?
Parathyroid disease frequently leads to osteoporosis, kidney stones, hypertension, cardiac arrhythmias, and kidney failure.
126
What is the most common treatment for primary hyperparathyroidism?
Surgery is the most common treatment for primary hyperparathyroidism.
127
What causes Secondary hyperparathyroidism?
Secondary hyperparathyroidism occurs as a result of another disease that initially causes low levels of calcium in the body, leading to increased parathyroid hormone levels over time.
128
What is the most common cause of Hypoparathyroidism?
Hypoparathyroidism is most commonly secondary to surgery.
129
What are some symptoms of Hypoparathyroidism and low calcium levels?
Symptoms include an unpleasant tingling sensation around the mouth and in the hands and feet, muscle cramps, and severe spasms known as 'tetany' that affect the hands and feet.
130
What emergencies can arise from low calcium levels in Hypoparathyroidism?
Emergencies can include seizures, severe irregularities in the normal heart beat, and spasm of both the upper and lower airways (laryngospasm and bronchial constriction).
131
Why could the Pancreas be legitimately described as both a secondary and primary endocrine organ?
The pancreas has both important exocrine function and primary endocrine function.
132
What prevalent endocrine disease arises from exocrine dysfunction of the pancreas?
Exocrine dysfunction of the pancreas gives rise to diabetes mellitus.
133
Is the pancreas an intraperitoneal or retroperitoneal structure?
The pancreas is a retroperitoneal structure.
134
What are the components (parts) of the Pancreas?
The components of the pancreas are the head, uncinate process, neck, body, and tail.
135
What are the endocrine glands of the Pancreas embedded in?
The endocrine glands are embedded in Islets of Langerhans throughout the gland.
136
Where are the Islets of Langerhans most numerous in the pancreas?
They are most numerous towards the tail of the gland.
137
What percentage of the pancreas mass do the Islets constitute?
The Islets constitute 1-2% of the mass of the pancreas by volume.
138
What percentage of the blood flow in the pancreas do the Islets receive?
They receive 10-15% of the blood flow in the gland.
139
What arteries supply the body of the Pancreas?
The body of the pancreas is supplied by branches of the splenic artery, commonly with a dominant branch called the arteria pancreatica magna.
140
What arteries supply the head of the Pancreas?
The head is supplied by the anterior and posterior superior and inferior pancreaticoduodenal arteries from the gastroduodenal and SMA.
141
What is the venous drainage of the Pancreas?
Venous drainage is into the SMV and splenic vein, and hence to the hepatic portal venous system.
142
What are the three different pathways providing nerve supply to the Pancreas?
Nerve supply is from the vagus nerve (CN X), thoracic splanchnics giving sympathetic supply, and fibres from coeliac and superior mesenteric plexuses.
143
What is Type 1 diabetes mellitus caused by?
Type 1 diabetes mellitus is due to pancreatic endocrine failure.
144
Can pancreatic exocrine disease or tumours lead to endocrine failure?
Yes, pancreatic exocrine disease such as pancreatitis, as well as some exocrine tumours causing duct obstruction, can lead to endocrine failure.
145
What are Neuroendocrine tumours of the pancreas (NET)?
NETs are tumours of the islet cells. They can be benign or malignant and tend to grow slowly.
146
What does it mean for a NET to be 'functioning'?
Functioning NETs are those that are producing hormone.
147
What is the commonest functioning NET of the pancreas?
The commonest NET is insulinoma.
148
How are the islets in the pancreas vascularized?
The islets are highly vascularized and arranged in a trabecular pattern, with a dense network of fenestrated capillaries.
149
What is the role of the fenestrated capillaries in the islets?
Fenestrated capillaries enable transport of substrates between the islet cells and the circulation.
150
What type of information do parasympathetic afferent fibres from the vagus nerve convey from the pancreas?
Parasympathetic afferents convey sensory information from ducts, acini and islets.
151
Where are the cell bodies of preganglionic vagal efferents supplying the pancreas located?
Their cell bodies are in the dorsal motor nucleus of the vagus.
152
Where do visceral afferents from the pancreas transmit pain and sensory information to?
Visceral afferents transmit pain and other sensory information to cell bodies in the sixth to twelfth thoracic dorsal root ganglia via the coeliac plexus and thoracic splanchnic nerves.
153
Where are the Adrenal (or suprarenal) glands located?
The adrenal glands are paired retroperitoneal glands situated medial aspect of the superior poles of each kidney.
154
Describe the typical shape of the right and left adrenal glands.
The right is pyramidal and the left is more crescenteric (or semilunar).
155
What encloses the adrenal glands along with the kidneys, and what does this structure attach them to?
The adrenal glands are enclosed by the perinephric fascia with the kidneys, which attaches them to the diaphragmatic crura.
156
What are the three main arterial sources of blood supply to the Adrenal Glands?
The three main arterial sources are the superior adrenal arteries (from the inferior phrenic artery), the middle adrenal artery (from the abdominal aorta), and the inferior adrenal artery (from the renal arteries).
157
Where does the left adrenal vein drain?
The left adrenal vein drains directly into the left renal vein.
158
Where does the right adrenal vein drain?
The right adrenal vein drains directly into the inferior vena cava.
159
What is the lymphatic drainage of the Adrenal Glands?
Lymphatic drainage is from 2 plexuses draining to the lumbar group of lymph nodes.
160
What provides sympathetic innervation to the adrenal medulla?
Sympathetic innervation to the adrenal medulla is by myelinated pre-synaptic fibres from T10-L1.
161
The adrenal medulla is considered the equivalent of what part of the sympathetic nervous system?
The adrenal medulla is the equivalent of the postsynaptic part (being derived from neuroectoderm).
162
What conditions can result from overproduction of adrenal hormones?
Overproduction can lead to Cushing’s syndrome (excess cortisol) or hyperaldosteronism (Conn’s syndrome).
163
What conditions can result from underproduction of adrenal hormones?
Underproduction can lead to Addison’s disease (insufficient cortisol) or hypoaldosteronism.
164
What type of tumour arises from the adrenal medulla, and what can it cause?
Tumours of the medulla called pheochromocytoma can lead to excessive catecholamines and result in hypertension.
165
Is there a universally agreed-upon fascial partition separating the kidney and ipsilateral adrenal gland within the perirenal fascia?
The existence of a fascial partition separating the kidney and ipsilateral adrenal gland within the perirenal fascial envelope is still debated.
166
What functions do the Testes perform?
The testes are both endocrine and exocrine organs.
167
Where are the Testes located?
The testes consist of paired ovoid organs residing in the scrotum.
168
What are the two main coverings of the testes?
The coverings are the strong capsule, the tunica albuginea, and the overlying tunica vaginalis (derived from the peritoneum).
169
What are the main components of the testicular parenchyma?
The parenchyma is composed of lobules draining to the rete testis, and thence into the epididymis.
170
What are the parts of the epididymis?
The epididymis has a head, body, and tail (caput, corpus, and cauda).
171
How do the testes reach the scrotum during embryonic development?
During embryonic development, the testes develop on the posterior abdominal wall and 'descend' through the inguinal canal to the scrotum.
172
What is the main arterial supply to the testis and epididymis?
The main arterial supply is by the testicular arteries arising from the aorta and passing through the inguinal canal.
173
What are the minor arterial supply sources to the testis?
Minor supply comes from the vasal artery (artery to vas deferens) and the cremasteric arteries.
174
From where does the vasal artery originate?
The vasal artery is a branch of the superior (occasionally inferior) vesical artery.
175
From where does the cremasteric artery originate?
The cremasteric artery is a branch of the inferior epigastric artery.
176
What is the venous drainage of the Testes?
Venous drainage is by the pampiniform plexus of veins around the testicular arteries.
177
Where do the testicular veins drain?
The testicular veins coalesce from the pampiniform plexus to drain into the IVC on the right and the left renal vein on the left.
178
What is the function of the pampiniform plexus arrangement?
The pampiniform plexus arrangement means that counterflowing arteries and veins permits the exchange of heat, facilitating the maintenance of lower testicular temperatures.
179
What structure provides innervation to the testes?
Innervation is from a plexus of nerves around the renal arteries and aorta.
180
How does the lymphatic drainage of the testis differ from that of the scrotal skin?
Lymphatic drainage of the testis follows the arterial supply to the para-aortic nodes, whereas the lymphatic drainage of the scrotal skin is to the inguinal nodes.
181
What is the appendix testis a remnant of?
The appendix testis is a remnant of the paramesonephric duct.
182
What is the appendix of the epididymis a remnant of?
The appendix of the epididymis is a remnant of the mesonephric duct.
183
What clinical symptom can twisting (torsion) of the appendix testis or appendix of the epididymis cause?
Both can twist (tort) and cause clinical symptoms.
184
Where are the Ovaries located?
The ovaries are paired ovoid organs situated in the pelvis.
185
How are the ovaries attached to the posterior aspect of the broad ligament?
They are attached by the fold called the mesovarium.
186
What structure is the mesovarium continuous with?
The mesovarium is continuous with the outer surface of the ovary.
187
What is the suspensory ligament of the ovary, and what does it contain?
The suspensory ligament of the ovary is a peritoneal fold extending to the pelvic wall, containing neurovascular structures including the ovarian artery and vein.
188
What ligament connects the ovary to the lateral cornu of the uterus?
The ligament of the ovary connects the ovary and the lateral cornu of the uterus.
189
What structure does the ligament of the ovary continue as?
The ligament of the ovary continues to the labium major as the round ligament.
190
What is the lymphatic drainage of the Ovaries?
Lymphatic drainage is via the para-aortic nodes.
191
What provides sympathetic innervation to the Ovaries, and at what spinal cord levels do the preganglionic fibres originate?
Innervation is from the sympathetic aortic plexus, with preganglionic fibres at T10 & T11 levels.
192
What is the function of the sympathetic fibres innervating the ovaries?
These fibres are vasoconstrictor.
193
Where is ovarian pain typically felt?
Sensory fibres accompany the sympathetic nerves, so ovarian pain is felt at the periumbilical area.
194
What provides parasympathetic innervation to the Ovaries?
Parasympathetic vasodilator fibres are from the inferior hypogastric plexus.
195
How do the location of the ovaries change during pregnancy?
During pregnancy, the ovaries are higher in the pelvis, becoming partly abdominal structures by 14 weeks and totally abdominal structures by the third trimester.
196
What is the epoopheron, and what is it a remnant of?
The epoopheron is a remnant of the mesonephric duct in the female reproductive tract, equivalent to the appendix of the epididymis in males.
197
Where can accessory ovarian tissue occur?
Accessory ovarian tissue can occur in the mesovarium and along the course of the gubernacular.
198
Where can ovaries rarely descend to?
Rarely, the ovaries may descend along the whole course of the gubernacula and are found in the labia majora.
199
What is the epoopheron a remnant of?
The epoopheron is a remnant of the mesonephric duct in the female reproductive tract, equivalent to the appendix of the epididymis in males.
200
What are some imaging modalities that may be employed to assess the endocrine system?
Modalities include Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Nuclear Medicine, Ultrasound, Digital Radiography (X-RAY), angiography, and Interventional Radiology.
201
What are the main uses of imaging in assessing the endocrine system?
Imaging is used to (1) assess function, (2) locate, evaluate and measure known or suspected lesions or tumours, and (3) allow image-guided biopsy of suspicious lesions or tumours.
202
How does imaging directly impact clinical decision-making in endocrinology and endocrine surgery?
Imaging directly impacts clinical decision-making. Image-guided fine-needle aspiration techniques for cytological diagnosis are also very valuable.
203
What imaging modality was used in the past to visualise larger pituitary adenomas?
In the past, some macroadenomas could be visualised on skull X-ray.
204
What is often the first detailed imaging investigation for symptoms like headache or visual disturbance that might indicate pituitary pathology?
CT is often the first detailed imaging investigation.
205
What is now the preferred imaging investigation to assess pituitary or hypothalamic pathology?
MRI is now the preferred imaging investigation.
206
What is a useful initial imaging modality for assessing the thyroid gland?
Ultrasound is a useful modality for this initial evaluation.
207
How should the normal thyroid appear on ultrasound?
The normal thyroid should be homogeneous in echotexture, and the two sides connected by an isthmus should be seen.
208
What changes in echotexture on ultrasound need investigating?
Changes in echotexture (hypo or hyperechogenicity) need investigating, although some nodules may be isoechoic.
209
What ultrasound technique can be combined with B-mode imaging for thyroid assessment?
Assessment can be combined with colour flow Doppler.
210
What finding on thyroid ultrasound can be a sign of potential malignancy?
Calcification may also be evident and can be a sign of potential malignancy.
211
What technique can allow sampling of thyroid nodules for cytological assessment?
Ultrasound guided Fine Needle Aspiration (FNAC) of nodules can allow sampling.
212
Are CT and MRI better than ultrasound for characterising thyroid nodules?
No, CT and MRI are not as good as ultrasound for characterizing thyroid nodules; small carcinomas readily identified by ultrasound may be undetectable on CT or MRI.
213
What is the main role of CT and MRI in thyroid imaging?
Their main role is to demonstrate extrathyroidal tumour extension, including extension of the gland into the chest for large thyroid masses.
214
What isotopes are used in Thyroid scintigraphy (Nuclear Medicine)?
Thyroid scintigraphy uses Iodine-123 or Technisium-99m.
215
What can Thyroid scintigraphy be used to evaluate?
Thyroid scintigraphy is used to assess: functional status of a nodule, differential diagnosis for thyrotoxicosis, assessment of thyroid cancer (whole body scan for distant metastases, estimation of local residual thyroid after thyroidectomy, follow-up for tumour recurrence).
216
What is the chance of a single 'cold' nodule being malignant on scintigraphy?
A single 'cold' nodule has a 10% chance of being malignant.
217
What is the chance of a single 'hot' nodule being malignant on scintigraphy?
A single 'hot' nodule has <1% chance of being malignant.
218
What are the predominant imaging techniques used for visualising the parathyroids?
Predominantly ultrasound and nuclear medicine are used.
219
When are CT and MRI usually reserved for parathyroid imaging?
CT and MRI are usually reserved to confirm the position of ectopic parathyroid adenomas anatomically.
220
What is the most common radiotracer for parathyroid imaging in Nuclear Medicine?
Tc-99m sestamibi is the most common radiotracer.
221
How does Tc-99m sestamibi uptake differ between normal and abnormal parathyroid glands?
Tc-99m sestamibi is taken up by abnormal parathyroid (high mitochondria in adenomas and hyperplasia), but Normal parathyroid glands do not take up sestamibi.
222
Can the adrenal glands be visualised on ultrasound?
Although they can be visualised on ultrasound, they are often difficult to see.
223
Is ultrasound the preferred modality for adrenal gland assessment?
No, ultrasound is not the preferred modality for assessment.
224
How are the adrenal glands typically visualised on CT?
The adrenals can be well visualised on CT and enhance with iv. contrast agents.
225
Describe the typical appearance of the right adrenal gland on CT.
The right gland appears as a linear, V-shape and is located superior and anteromedial to the upper pole of the right kidney.
226
Describe the typical appearance of the left adrenal gland on CT.
The left gland appears as a triangular or Y-shape and is located superior and anteromedial to the upper pole of the left kidney.
227
For what specific assessment are different MRI protocols useful for the adrenal glands?
Different MRI protocols are useful for assessment of fat content, e.g., suspected adenomas (lipid poor) and fatty myelolipoma.
228
What is Adrenal Vein Sampling (AVS)?
AVS is a procedure where blood is collected from the adrenal veins via catheter to confirm autonomous hormone production, determine if it is unilateral or bilateral, and guide treatment.
229
What Nuclear Medicine scan is used in the investigation of phaeochromocytoma?
The scintigraphic study, MIBG scan (metaiodobenzylguanidine), is used.
230
What other conditions can an MIBG scan be positive in?
It can also be positive in neuroblastoma, carcinoid, medullary thyroid cancer and ganglioneuromas.
231
What are pancreatic neuroendocrine tumours (pNETs) and where do they arise from?
pNETs are endocrine tumours of the pancreas that arise from the islet cells.
232
What are some distinct types of functioning pNETs mentioned?
Distinct types include Insulinoma, Gastroma, Glucagoma, and non-functioning types.
233
How may pNETs be seen on transabdominal ultrasound?
They may be seen as hypoechoic, circumscribed round or oval lesions.
234
Why is Endoscopic ultrasound (EUS) often preferred for visualising the pancreas compared to transabdominal ultrasound?
Bowel gas makes transabdominal examination difficult. EUS allows the transducer to be placed closer to the pancreas, providing higher frequency and better resolution.
235
What additional technique is possible with Endoscopic ultrasound?
EUS also allows FNAC.
236
How do CT scans visualise pancreatic endocrine tumours?
CT can visualise pNETs as hypervascular, well circumscribed lesions.
237
How might larger pNETs appear on CT?
Larger tumours may have signs of necrosis and thus appear heterogenous.
238
What is the sensitivity of MRI compared to CT for detecting pNETs?
MRI has similar sensitivity to CT for detecting pNETs.
239
What role do Nuclear Medicine scans have in evaluating pNETs?
Nuclear medicine scans have an important role in evaluating pNETs, allowing functional imaging.
240
What specific Nuclear Medicine scans are used for pNETs?
Octreotide scans or Gallium-68 DOTATATE scans combined with CT (PET-CT) are used.
241
What are the two functional states described for endocrine glands in relation to hormone production?
Endocrine glands can over produce their hormones (hyperfunctioning) or under produce (hypofunctioning).
242
What should one be aware of in clinical studies regarding multiple endocrine tumours?
One condition to be aware of is multiple endocrine neoplasia (MEN).
243
What are some general characteristics of MEN?
MEN have different types with distinct syndromes and clinical presentation. Some tumours may be benign and others malignant.
244
What endocrine glands are typically involved in MEN 1 (Wermer Syndrome)?
MEN 1 involves Parathyroid tumours, pancreatic endocrine tumours and pituitary tumours.
245
What endocrine glands/tumours are typically involved in MEN 2a?
MEN 2a involves Medullary thyroid cancers (parafollicular cells), phaeochromocytoma and parathyroid tumours.
246
What endocrine glands/tumours are typically involved in MEN 2b?
MEN 2b involves Medullary thyroid cancers (parafollicular cells), phaeochromocytoma and neuroma.
247
What type of genetic disease is Wermer syndrome (MEN 1)?
Wermer syndrome is an autosomal dominant genetic disease.
248
What does Wermer syndrome result in?
Wermer syndrome results in proliferative lesions in multiple endocrine organs, particularly the pituitary gland, pancreas, and parathyroid glands.
