Endocrinology Anatomy Flashcards
What is the anatomical position of the adrenal glands?
Superiomedially between the superior pole of the kidney and the crus of the diaphragm
What is the embryological origin of the cortex?
Mesoderm (similar to the gonads)
What is the embryological origin of the medulla?
Ectoderm (similar to the SNS)
What does the adrenal cortex secrete?
Steroid hormones
Mineralocorticoids (aldosterone)- electrolyte and fluid homeostasis
Glucocorticoids (cortisol) - CHO, protein, and lipid metabolism
Sex hormones - testosterone and oestrogen
What does the adrenal medulla secrete?
Catecholamines: (nor)adrenaline
What regulates glucocorticoid secretion?
Anterior pituitary adrenocorticotropic hormone (ACTH)
What regulates mineralocorticoid secretion?
RAAS and [K]plasma
What regulates secretion of medullary catecholamines?
SNS
Chromaffin cells
Thorcacic splanchnic nerves
Coeliac Plexus
What the the two layers of the adrenal gland?
Outer cortex
Inner Medulla
What invests the adrenal gland?
Dense fibrous capsule
What are the 3 layers of the adrenal cortex and what are their functions?
Remember GFR
- Zona Glomerulosa: large amounts of sER and mito; secretes mineralcorticoid hormones (aldosterone) controlled by RAAS and [K]plasma, RAAS is regulated by the macula densa
- Zona Fasciculate: middle and broadest; cytoplasm rich in sER, mito, and lipids; secretes glucocorticoids (cortisol); Also secretes sex hormones
Zona Reticularis: inner most; fewer lipid droplets; secretes small quantities of androgens and glucocorticoids
How is aldosterone release triggered?
- Decreased arterial pressure
- Decreased GFR
- Decreased macula densa NaCl
- Increased renin production
- RAAS pathway
Where, in the kidney, does aldosterone act on?
Renal tubules
Increases Na+ and H2O retention
In turn increasing ECF volume and arterial BP
Can aldosterone secretion be triggered by ACTH?
No
What controls cortisol secretion?
Hypothalamus (CRH) –> Anterior Pituitary (ACTH) –> Adrenal Cortex (Cortisol)
Hypothalamus stimulus: stress, time of day, illness
What is the medulla composed of?
Closely packed clusters of secretory cells
What does the medulla secrete?
Catecholamines: (nor)adrenaline
What forms the endocrine pancreas?
Islets of Langerhans
Where are the islet of Langerhans found?
Scattered throughout the exocrine glandular tissue
Vary in size
MOST NUMEROUS in tail of pancreas
What cells comprise the endocrine pancreas?
B-cells (70%) - secrete insulin in response to hyperglycaemia –> Promotes glucose uptake by GLUT4
A-cells (25%) - secretes glucagon –> respond to hypoglycaemia
D-cells (4%) - secrete somatostatin –> GI Function + inhibit alpha and beta-secretion
PP-cells (1%) - secrete polypeptide hormone
What kind of hormone is insulin?
Peptide
Where is insulin synthesised?
Describe the pathway
- b-cells of pancreas
- at eER as preproinsulin
- preproinsulin is cleaved to form proinsulin
- proinsulin is then cleaved at the Golgi to form insulin
- insulin is then packages in vesicles and remains in the cytoplasm for secretion
Where does the pancreas lie?
Retroperitoneal
Transversely across the posterior abdominal wall
Posterior to the stomach
Between the duodenum on the right and the spleen on the left
What lies on the anterior margin of the pancreas?
Root of the transverse mesocolon
Where does the exocrine secretions of the pancreas come from?
Pancreatic juice from acinar cells, which enters the duodenum
Where is the pancreas positioned relative to the duodenum
Head of pancreas is embraced by the C-shaped curve of duodenum
How is the uncinate process of the pancreas positioned?
Inferior to the head of the pancreas, extends medially to the left, posterior to the SMA/V
What structure do the pancreatic and common bile ducts form? and where?
Hepatopancreatic amuplla (of Vatar), which opens into the descending duodenum at the greater dudenal papilla (8-10cm from pylorus)
What structure controls secretions of the pancreas and gall bladder?
Sphincter of Oddi
CCK cause it to relax (and cause gallballder to contract)
Where do the pancreatic arteries branch of?
Splenic artery
Main: Greater pancreatic artery
What is the pancreatic venous drainage?
Pancreatic veins are tributaries of the splenic and SM parts of the hepatic portal vein
Most empty into the splenic vein
What is the functional unit of the exocrine pancreas
Pancreatic acini
What type of epithelium lines the exocrine pancreatic ducts?
Simple cuboidal
Larger ducts: stratified cuboidal
What do the cells in the pancreatic duct secrete?
Water and HCO3-
How many layers of fascia and fat are they kidneys surrounded by? And name them.
Perinephric fat (capsule) - surround the kidneys and adrenal glands and is continuous with the renal sinus, enclosed by a membranous layer
External to the fascia is the paranephric fat
Where are the adrenal glands located?
Between the superiomedial aspects of the kidneys and the diaphragmatic crura, where they are surrounded by connective tissue containing perinephric fat
Of what type of tissue is the capsule of the adrenal glands formed?
Fibrous connective tissue
What tissue lies outside the capsule?
Loose connective tissue containing white fat (unilocular adipose tissue)
It’s called perinephric fat
The cells forming the zona fasciculate appear pale in H&E stained section and contained empty, small rounded profiles. What is an alternative name for these cells?
Spongiocytes
A spongiocyte is a cell in the zona fasciculata of the adrenal cortex containing lipid droplets that show pronounced vacuolization
What is the diameter of a RBC?
7-8micrometers
What receives blood first the medulla or the cortex?
The medulla receives blood first from the capillaries and the sinusoids of the adrenal cortex second from arterioles passing from the capsule to the medulla
Where does the pancreas lie?
Retroperitoneal in the “stomach bed”
What type of capillaries are in the Islets of Langerhans
Fenestrated
What is the GTT important for?
Diagnosing of disorders of CHO metabolism
What are the main target tissues for insulin?
Muscle and adipose tissue
Blood glucose will be elevated after ingestion of a fixed dose of glucose.
After how long would the [glucose]blood take to return to normal?
What about a diabetic person?
Within 2 hours
Diabetic: significantly longer
What enzyme is used in ExacTech Blood Glucose Monitoring systems?
Glucose oxidase
What happens to glucose as it is filtered by the kidney?
Reabsorbed by SGLT2 (90%) at the PCT and SGLT1 (10% at the descending loop of Henle at the apical lumen, and into the blood via GLUT2 at the basolateral surfaces.
What is the normal concentration of glucose in the urine?
0-0.8mmol/L
What is the glucose reabsorption threshold? And what happens if this is exceeded?
10.0mmol/L
Glucosurea
What hormones/neurotransmitters increase by the procedure of taking blood?
Stress hormones
GH, adrenaline(nor), and cortisol
ACh
Which tissues metabolise glucose and what do they form?
Liver: glycogen
Muscle: glycogen
Adipose: triglycerides
How would the metabolism of glucose change as your body glucose concentration returns to resting values?
Increase glycogen synthesis
Decreased blood glucose levels
What tissues are totally dependent on glucose as an energy source? And why?
Brain - due to blood-brain barrier
RBCs - don’t have mitochondria for oxidation and energy production from alternative substrates
Testes - blood testis barrier
What different types of glucose transporters are found in the body? Which are in the kidneys?
GLUTs 1-5
SGLTs 1-2
Kidney:
SGLT1/2 and GLUT2
What effect would you expect if an average meal were accompanied by oral administration of an inhibitor of alpha-glucosidase activity?
Alpha-glucosidase is inhibited by acrabose
This drug is an inhibitor of this enzyme which normally digests complex sugars (starch) and delays intestinal absorption of glucose.
Side effects? gas.
What drug inhibits alpha-glucosidase? and how.
Acrabose
Why might a patient with diabetes have [glucose]>11mM after an overnight fast?
Decreased insulin
Gluconeogenesis increases blood glucose.
Why do diabetic patients tend to have nocturnal polyuria?
Glucose in the urine exerts osmotic pressures in the filtrate resulting in polyuria.
- Plasma glucose high
- Glucose filtered in the kidneys
- Glucose in filtrate exceeds reabsorptive capacity (>10mmol/L)
- Glucose in the tubule creates osmotic gradient and draws water into the filtrate.
- Polyuria.
Why do patients with T1DM lose weight while eating plenty?
No insulin is produced at all
Lack of glucose in the cells
Catabolism of FA/AA
Where does the adenohypophysis develop from?
dorsal outgrowth from the wall of the embryonic pharynx
Where does the neurohypophysis develop from?
Down growth from the diencephalon
What surrounds the pituitary gland?
Fibro-elastic capsule
Where does the the fibrous capsule of the pituitary gland develop from?
Innermost meneges layer
Dura
Primitive pia matter
In the adenohypophysis there are two types of secretory cells. What are they? And what do they represent?
Chromophobes - pale; exhausted secretory cells
Chromophils - dark; actively secreting cells
In H&E staining, what do basophils bind to and what colour are they?
Basic stains (haematoxylin) Dark purple colour
In H&E staining, what do acidophils bind to and what colour are they?
Eosin (acidic dye)
Red
How many different endocrine cells are found within the adenohypophysis?
5
List the endocrine cells found within the adenohypophysis and their %
- Somatotrophs - 50% - Secrete growth hormone
- Lactotrophs - 20% - Secrete prolactin
- Corticotrophs - 10-15% - Secrete: POMC
- Adrenocoticotropic hormone (ACTH)
- b-lipotropin hormone (b-LPH)
- a-melanocyte stimulating protein (a-MSH)
- b-endorphin - Tyrotrophs - 5% - Secrete thyroid stimulating hormone (TSH)
- Gonadotrophs - 10% - Secrete FSH and LH
What type of capillaries are found within the adenohypophysis?
Fenestrated Capillaries
Where does the thyroid gland develop from?
Thyroid gland develops from an ENDODERMAL downgrowth (the ‘thyroglossal duct’) from the floor of the developing pharynx
Derived from the base of the tongue
Thryoglossal duct
Passing through the hyoid bone
What marks the site of down growth of the thyroid gland?
Foramen caecum at the back of the tongue
Describe the gross structure of the thyroid gland
Two lobes connected by a midline isthmus
Histologically what does the thyroid gland consist of?
Follicles
Where is the thyroid?
Anterior neck
Wrapper in front of larynx
Whats the weight of the thyroid?
approx. 20g
What type of cells are thyroid follicles?
Epithelial structures
Simple
- Inactive follicles: low cuboidal or squamous
- Active follicles: columnar
What hormones are synthesised in the follicles?
- Thyroxine (T4)
2. Tri-iodothyronine (T3)
How does the thyroid cells concentrate iodide?
Iodine pump
What hormone regulates the activity of the thyroid gland and where is it produced?
Thyroid releasing hormone (TRH) by the hypothalamus
Which cell organelle produces the protein part of thyroglobulin?
eER
Which cell organelle adds the sugar component to thyroglobulin?
Golgi Apparatus
In the thyroid, what is colloid?
Iodinated glycoprotein, rich in thryoglobin, is a storage form of thyroxine
Thyroid
Which enzyme, synthesised by the follicle cell, enables iodide to be converted to iodine?
Thyroid peroxidase
How is thyroglobulin taken up by thryoid cells?
Pseudopodial extensions of the cytoplasm enclose droplets of thyroglobulin and bring them into the cell when thyroxine and tri-iodothyronine are required
Where is thyroglobulin stored in the thyroid?
Colloids
What is Hasimoto’s disease? How is it caused?
- Hashimoto’s thyroiditis is an autoimmune disease
- The thyroid is underactive
- Patient is described as having hypothyroidism
- Condition results because of antibodies to thyroid peroxidase (antimicrosomal antibodies) are produced
- Infiltration of plasma cells, lymphocytes, macrophages
- Germinal centre formation
- Oncocytic change in epithelium (Hurthle cells)
Where would you find Hurthle cells? And what are they?
Hashimoto’s thyroiditis
Hurthle cells = oncocytic change in epithelium
Define glycoprotein
Any of a class of proteins which have carbohydrate groups attached to the polypeptide chain.
What are colloids?
Found within thyroid follicles
Storage form of thyroid hormones T3/T4
Contain several enzymes
What is the major chemical component of colloid
Thyroglobulin, an iodinated glycoprotein containing about 120 tyrosine residues
How many and what are the hormones released by follicular epithelium of the thyroid?
Follicular cells:
- Tri-iodothyronin (T3)
- Thyroxine (T4)
Parafollicular cells (C-Cells) 1. Calcitonin
Where are T3/T4 derived from?
T3 and T4 are iodinated derivatives of tyrosine
Which is functionally more important T3 or T4?
T3
What do thyroid follicular cells mainly produce? T3 or T4?
T4
What triggers the hypothalamus to produce TRH?
Low levels of thyroxine (T4) in circulating blood
What is the main function of T3 and T4?
Regular cell and tissue basal metabolism
Define basal metabolic rate
The rate at which the body uses energy while at rest to maintain vital functions such as breathing and keeping warm.
What is a sign of hypocalcaemia?
Twitching of face and arm muscles
What other biochemical change can result from hypocalcaemia? And what can this cause?
Hyperphosphataemia
Severe itching and weakening of the bones
What do C-cells (parafollicular cells) in the thyroid release?
Calcitonin
Summaries the function of calcitonin
Released in response to elevated blood calcium levels
Reduces calcium levels in the blood by:
- Inhibiting the activity of osteoclasts
- Promotes absorption of calcium by bone
- Decreases reabsorption of calcium in the kidneys
What is the role of osteoclasts?
Bone resorption
They are large multinucleated cells
What is the normal serum concentration of calcium?
2.25-2.5mmol/L
What hormones regulate blood calcium? And how do they do it?
Calcitonin - respond to increased calcium
PTH - respond to decreased calcium
Where is PTH secreted from?
Parathyroid gland
Chief cells
Where is the parathyroid gland located?
Posterior to the thyroid gland or sometimes embedded within the thyroid gland
What types of cells are found in the parathyroid glands?
2 types of secretory cells
- Chief cells - secrete PTH
- basophilic - Oxyphil cells
- acidophilic
1 other cell
- Water-clear cell: just chief cells with pools of glycogen
How may parathyroid glands are there? And what is their weight?
4
120mg - combined weight
Does the parathryoid gland posses a connective tissue capsule?
Yes
Thin fibrous capsule
Where doe the parathyroid glands come from emrbyologically?
- upper pair: from 4th brachial cleft (phayngeal pouches) and descend with thyroid
- lower pair: from3rd brachial cleft and descend with thymus
Where does the external jugular vein run?
EJV runs vertically across the sternocleidomastoid muscle towards the neck of the mandible
How could you make the external jugular vein prominent ?
Take a deep breath in makes the vein prominent
Valsalva maneuver
What lies between the sternal heads of the sternocleidomastoid muscles?
Jugular notch of manubrium
Where does the internal jugular vein lie?
Lesser supraclavicular fossa between the sternal and clavicular heads of the sternocleidomastoid muscle - overlies the end of the IJV
What is the carotid sheath and where does it lie?
IJV + common carotid + vagus
Lies deep to the inferior half of the sternocleidomastoid muscle
What lies deep to the superior half of the sternocleidomastoid muscle?
Cervical plexus
What muscles lie superior and inferior to the hyoid bone
Suprahyoid muscles
- Mylohyoid muscle
- geniohyoid muscle
- stylohyoid muscle
- digastric muscle - ant. and post. belly
Infrahyoid muscles
- sternohyoid
- omohyoid
- sternothyroid
- thyrothyroid
Where does the thyroid gland lie relative to the trachea and larynx?
Anterolaterally
R and L lobes
What vertebrae level does the thyroid gland lie?
C5-T1
What lies in the anterior neck
put in order
thyroid
thyroid cartilage
trachae
cricoid cartilage
Superiorly
- Thyroid cartilage
- Cricoid cartilage
- Thyroid gland
- Trachea
What is the cricoid cartilage?
Only complete ring of cartilage around he trachea
Sits inferior to the thyroid cartilage and superior to the thyroid
IT IS NOT THE 1ST TRACHEAL RING
What is the arterial blood supply to the thyroid? And where do they arise from?
- Superior thyroid artery- arises from external carotid artery
- Inferior thyroid artery - arises from subclavian artery (branches of thyrocervical trunks
What is the venous drainage of the thyroid?
3 Pairs of thyroid veins usually rain the thyroid plexus of veins on the anterior surface of the thyroid gland and trachae
- Superior thyroid vein - drains into internal jugular vein
- Middle thyroid vein - drains into internal jugular vein
- Inferior thyroid vein - drains into the brachiocephalic veins posterior to the manubrium
What is the nervous innervation to the thyroid?
Branches of the vagus
- Superior laryngeal Nerve
- internal branch
- external branch - Left recurrent laryngeal nerve
What is the anatomical position of the larynx and at what vertebrae levels?
Complex organ of voice production
Anterior neck at level C3-C6
Connects oropharynx with trachea
What is the most important function of the larynx?
Guard the air passage, especially during swallowing, where it serves as a sphincter/valve of the lower respiratory tract, thus maintaining a patient airway
What is the laryngeal skeleton composed of?
9 cartilages joined together by ligaments and membranes
- 3 cartilages are single: thyroid, cricoid, epiglottic
- 3 cartilages are paired: arytenoid, corniculate, and cuneiform (posterior aspect)
Which vertebral bodies lies the thyroid cartilage?
C4
What does the median plan of the thyroid cartilage form?
Laryngeal prominence (Adam’s apple)
How does the thyroid cartilage attach to the hyoid bone?
- Thyrohyoid membrane (superiorly)
- Thyrohyoid ligaments (medial and laterally)
How does the thyroid cartilage articular with the cricoid cartilage?
Inferior horn of the thyroid cartilage articulates with the lateral surface of the cricoid cartilage at the cricothyroid joints
What is the posterior and anterior surfaces of the cricoid cartilages called?
Posterior: lamina
Anterior: arch
What surrounds the laryngeal ventricle?
Laryngeal ventricle
- recesses extending laterally from the middle part of the laryngeal cavity between the vestibular and vocal folds
What are the vocal folds?
True vocal cords
Control sound production
What is the action of the platysma muscle?
Draws corners of the mouth inferiorly and widens it
Where does the platysma muscle arise from?
Arises in subcutaneous tissue covering the superior parts of the deltoid and pectolaris major and sweeps superiomedially over the clavicle into the inferior border of the mandible
