Pancreas and adrenal glands anatomy and histology

Question 1

Define exocrine

Answer 1

Cells secreting substances via ducts, which are then released onto epithelial surfaces

Question 2

Define endocrine

Answer 2

Cells producing hormones, which are released into the bloodstream (‘ductless’ glands) and act at distant sites

Question 3

Define Paracrine

Answer 3

Cells secreting chemical messengers, which act nearby

Question 4

Define autocrine

Answer 4

Cells secreting substances into the extracellular space, which then act upon the same cells which produced them

Question 5

Describe the embryology of the pancreas

Answer 5

Endodermal origin
Two buds extend from primitive duodenum at the junction of the foregut and midgut
They fuse together to form the pancreas and bile duct system

Question 6

Describe the anatomy of the pancreas

Answer 6

12-15cm long J-shaped organ
Retroperitoneal
Lies transversely on posterior abdominal wall
Behind the stomach
Across L1/L2 level
Tail lies in hilum of the spleen

Question 7

Briefly describe the histology of the pancreas

Answer 7

Lobulated gland

divided by fibrous septa

Question 8

Describe the histology of the exocrine gland of the pancreas

Answer 8

Main bulk of tissue

> Secretory acini

• densely packed cells with granular cytoplasm
• Produce digestive enzymes and watery alkaline fluid
• Tiny central lumen in each, draining to duct system

> Duct system

• highly branched system, converging to form pancreatic duct
• joins with the common bile duct to enter duodenum at ampulla of Vater
• cuboidal to columnar lining

Question 9

Describe the histology of the endocrine component of the pancreas

Answer 9

Small volume, important

> islets of langerhans

• small roundish collections of endocrine cells
• highly vascular due to endocrine role (for secretion of hormones into the blood)
• produce peptide hormones insulin, glucagon and some others including somatostatin

Question 10

Which cell types produce which hormones?

Answer 10

Beta cells - insulin
alpha cells - glucagon
delta cells - somatostatin

Question 11

What are the main disorders of the pancreas?

Answer 11

> Diabetes mellitus
Islet cell tumours
Pancreatitis
Pancreatic carcinoma

Question 12

Describe DM

Answer 12

Failure of the pancreatic islet cells to produce sufficient insulin to meet the metabolic needs of the body

T1DM (IDDM)

• autoimmune destruction of islet cells
• absolute deficiency of insulin

T2DM (NIDDM)

• tissue resistance to effects of insulin
• relative insulin deficiency (obesity - more tissue to supply)

Question 13

Describe islet endocrine tumours

Answer 13

Rare disease
Neoplastic proliferation of endocrine cells of pancreatic islets
May produce hormones such as insulin, glucagon and somatostatin
Patients can present with symptoms due to excessive quantities of hormone
- e.g. recurrent episodes of hypoglycaemia with insulin excess

Question 14

Describe pancreatitis

Answer 14

Inflammation of the pancreas
Different types:

> Acute pancreatitis:

• serious life-threatening disease, sudden onset
• damage to pancreatic tissue releases dangerous digestive enzymes directly into surroundings

> Chronic pancreatitis

• may follow repeated episodes of acute damage
• causes scarring and loss of normal tissue
• leads to malabsorption (exocrine-type disease) and risk of secondary diabetes

Question 15

Describe pancreatic carcinoma

Answer 15

Malignant tumour of the pancreas, poor prognosis
Most commonly affects head of pancreas
- presents acutely with obstructive jaundice by blocking common bile duct
- may invade into adjacent structures, such as stomach, duodenum, transverse colon and major vessels
- very difficult to remove surgically - usually only possible if diagnosed early
- can spread to lymph nodes, liver and peritoneal cavity

Body or tail of pancreas

• often few symptoms until late disease
• may present with metastases

Question 16

Describe the embryology of the adrenal glands

Answer 16

different embryological origins, seperate glands in different animals

> Cortex

• mesodermal, from urogenital ridge
• before birth, foetal zone with large eosinophilic cells
• postnatally, this involutes and outer layer forms the definitive cortex with three zones

> Medulla

• Derived from neural crest cells (ectodermal)
• Part of sympathetic nervous system (effectively a large ganglion)

Question 17

Describe the anatomy of the adrenal glands

Answer 17

Paired organ in retroperitoneum
5-8g
situated above upper poles of kidneys (suprarenal glands)
anatomically and functionally divided into 2 parts
- outer cortex
- inner medulla
Gerota’s fascia (fibrous tissue) - capsule encapsulating kidneys and adrenal glands

Question 18

Describe the histology of the cortex

Answer 18

Three layers:

> Zona glomerulosa
Zona fasciculata
Zona reticularis

Question 19

Describe the histology of the zona glomerulosa

Answer 19

Outer layer of adrenal cortex
produces aldosterone
discontinuous

Question 20

Describe the histology of the zona fasciculata

Answer 20

80% of the cortex of the adrenal glands
lipid-rich (cholesterol for steroid hormones)
glucocorticoids and androgens

Question 21

Describe the histology of the zona reticularis

Answer 21

Like fasciculata but less lipid therefore cells pink, less clear

Question 22

Describe the histology of the adrenal medulla

Answer 22

Central area, part of sympathetic nervous system
Produces adrenaline and noradrenaline (~5:1)
Released in response to physiological stressors
Diverse effects, part of ‘fight or flight’ response

Question 23

Name the layers of the adrenal medulla

Answer 23

> Glomerulosa - balls of cells
Fasciculata
Reticularis - network/meshwork of cells
Medulla

Question 24

Describe the histology of the adrenal veins

Answer 24

Distinctive shape - muscle layer is not uniform all the way around
Surrounded by medullary cells

Question 25

List the common disorders of the adrenal glands

Answer 25

Adrenal adenoma
Adrenal cortical carcinoma
Atrophy
Phaechromoctyoma

Question 26

Describe adrenal adenoma

Answer 26

Benign tumours of the adrenal cortex
May produce excessive hormones
> Cortisol (Cushing's syndrome)
> Aldosterone (Conn's syndrome) = hypoaldosteronism
> Adrenal androgen excess

Patients may present with symptoms and signs due to hormonal excess
Rarely present with local symptoms due to often small growths
Often incidental finding on radiological imagine

Question 27

Describe adrenal cortical carcinoma

Answer 27

Rare disease
Malignant proliferation of cells of adrenal cortex
Less common to produce excess hormones (cells are less differentiated)
May invade into surrounding structures and spread (metastasise) to distant sites

Question 28

Describe adrenal atrophy

Answer 28

Decrease in functional mass of cortex
Often iatrogenic -> administration of corticosteroids, usually long term
Negative feedback blocks ACTH production
No stimulus for activity of cortical cells
Sometimes due to autoimmune destruction (addison’s disease)

NB: Addisonian crisis (= adrenal failure) can occur if you decrease steroid treatment suddenly

Question 29

Describe phaeochromocytoma

Answer 29

Uncommon tumour of adrenal medulla
Important cause of secondary hypertension
Produce catecholamines (adrenaline, noradrenaline)
Metabolites of these compounds can be detected in urine
Useful in diagnosis