Histology of glands lecture Flashcards
What type of tissue are glands made from?
Epithelial tissue
What are the two categories of glands?
Endocrine
Exocrine
What are the key features of endocrine glands?
Secretions are typically directly into the blood (hormones)
Generally have no ducts
Regulate bodily functions
What are the key features of exocrine glands?
Release substances directly onto an epithelial surface (unicellular) or use a system of ducts to indirectly release onto an epithelial surface (Multicellular)
What type of tissue typically surrounds gland ducts?
They invaginate into connective tissue
What are some examples of endocrine glands?
Hypothalamus
Pituitary
Parathyroid
Thyroid
Adrenal
pancrease (component of)
What is the location of the thyroid gland?
Loacted on the anterior neck
Seperated into right and left lobes connected by an isthmus
Describe the histological arrangement of a thyroid gland?
Follicular cells are simple cuboidal, these arrange themselves to form many follicles
Follicles contain colloid
Each follicle is surrounded by reticular fibres
Parafollicular cells are found peripherally in the basal lamina or between follicles
numerous capillaries are found surrounding the follicles
The gland is divided into lobules by connective tissue septa
In relation to the thyroid gland what is colloid?
Colloid is made of throglobulin
This is an inactive version of thyroid hormones (T3 and T4)
Is mainly iodinated glycoportein so stains eosinophilic
What is the role of parafollicular cells in the thyroid?
Also called C-cells
Secrete calcitonin in response to high blood calcium causes Ca2+ to move from the blood into the bone.
What control the pituitary gland?
The hypothalamus
What is the origin of the posterior pituitary gland?
Oringates from a neural downgrowth from the hypothalamus, to which is joints by the pituitary stalk.
What is the origin of the anterior pituitary gland?
Originates from epithelial (ectoderm) upgrowth from the roof of the oral cavity, known as rathke pouch
What are the two different embryonic origins of the pituitary gland?
What section does each origin become?
Adenohypophysis - pars distalis, pars tuberalis, pars intermedia
Neurohypophysis - pars nervosa and infundibulum/pituitary stalk.
What makes up the posterior pituitary gland?
The pars nervosa
The pituitary stalk
The pars intermedia
What makes up the anterior pituitary gland?
The pars disatalis
the pars tuberalis
What is the hypothalamo-hypophyseal tract?
White matter tract (axons) from nuclei in the hypothalamus to the posterior pituitary gland.
Supraoptic nuclei
Paraventricular nuclei
What is the function of pars distalis in the pituitary gland?
95% of the adenohypophysis
Forms the anterior wall of rathkes pouch
What is the role of pars intermedia in the pituitary gland?
Forms part of the posterior wall of rathke’s pouch (rest by pars nervosa)
What is the function of pars tuberalis in the pituitary gland?
Forms a collar of cells around the pituitary stalk
What is the remnant of rathkes pouch in the pituitary gland?
Part of the adenohypophysis
Shows that the pituitary gland grew upwards from the oral cavity ectoderm.
This seperates the pars intermedia from the rest of the adenohypophysis
How do the hypothalamux nuclei link to the pituitary gland?
Hypothalamus contains the paraventricular nucleus and the supraoptic nucleus
Signals travel down the pituitary stalk in the hypothalamic pituitary tract into the pars nervosa (posterior pituitary gland) .
Hormones are synthesised and stored then more impulses from the hypothalamus cause their release.
This is neurosecretion
What is the function of the hypothalmic nuclei linked to the pituitary gland?
Paraventricular nuclei - synthesise ADH/ vasopresin
Supraoptic nuclei - synthesise oxytocin
When looking at a sagital histological section of the pituitary gland in situ what structures need to be considered?
Distinguish between the posterior and anterior (basophilic) pituitary gland.
Pituitary stalk
Identify the hypothalamus
The third ventricle ( behind the hypothalamus)
The optic chiasm (large circular structure)
What is the name of the bony depression that the pituitary gland sits in?
THe sella turcica of the sphenoid bone
In regards to a histological image what is a key way to distinguish between the anterior and the posterior pituitary gland?
The posterior is more eosinophilis (lightly stained)
The anterior is more acidophilic (darkly stained)
How are the different cell types distributed in the pituitary gland?
Pars distalis contains all five types
The pars tuberalis contains gonadotropes only
What are the different cell types in the pituitary gland?
Sommatotrope
Mammotrope
Thyrotrope
Gonadrotrope
Adrenocortitrope
What cell types in the pituitary gland are acidophilic?
Sommatotrophe
Mammotrope
Give an example of the hormone secrete by sommatotrope cells?
Growth Hormone
Give an example of the hormone secrete by mammotrope cells?
Prolactine
Give an example of the hormone secrete by thyrotrope cells?
Thyroid stimulating hormone
Give an example of the hormone secrete by gonadotrope cells?
FSH and LH
Give an example of the hormone secrete by adrenocorticotrope cells?
ACTH
Explain how hormones are stored and released in the posterior pituitary gland?
Hormones accumulate in unmyelinated axons (extend from hypothalamus) called Herring bodies
When needs are released into fenestrated capillaries in surrounding pars nervosa
How is the release of hormones from the pituitary gland controlled?
By negative feedback mechanism that communicate with the hypothalamus
Where are the adrenal glands located?
Superior pole of each kidney
Surrounded by adipose tissue
How are the adrenal glands structured?
Surrounded by a dense irregular connective tissue capsule
Outer cortex
-zona glomerulosa
-zona fasiculata
-zone reticularis
inner medulla
What cell type makes up the cortex of the adrenal gland?
Steroid secreting cells
What cell type makes up the medulla of the adrenal gland?
Chromaffin cells (sympathetic cells derived from neural crest cells)
What are the key features of the zona glomerulosa in the adrenal cortex?
Immediatly deep to the capsule
Cells in round clusters
Secrete mineralcorticoids such as aldosterone
What are the key features of the zona fasiculata in the cortex of the adrenal gland?
Middle layer
Largest zone
Cells arranged in parallel rows
Secretes glucocorticoids and androgens
What is the location, cell type and hormones secreted by the zona reticularis in the adrenal cortex?
Deepest layer of the adrenal cortex
Cells are arranged as anastomosing cords
Secretes glucorticoids and androgens
What is the key way to distinguish between the different histological layers of the adrenal cortex?
Zona glomerulosa (means knot), cells are is circular clumps
Zona fasciculata - parallel row arrangement of cells, longest section
Zona reticularis - (net like) anastamosing cells with an empty centre.
Note zona reticularis is basophilic.
What are the different glandular functions of the pancreas?
Exocrine portion - alkaline secretions containing digestive enymes that empty into duodenum including proteases, carbohydrases and lipases
Endocrine portion - secretes insulin, glucagon and somatostatin that regulate blood glucose levels.
What structure do pancreatic ducts open into?
The duodenum
How does the cell type vary between the pancrease endocrine and exocrine ducts?
Endocrine - islet of langerhans
Exocrine - acinus cells
What is the function of islet of langerhans cell types?
Clumped masses of endocrine cells in the pancrease
Alpha cells - secrete glucagon
Beta cells - secrete insulin (this is the main cell type)
delta cells - secrete somatostatin
Away in a manjor, back off
What is the role of somatostatin?
Inhibits insuling, glucagon and somatotropin hormone
What are the tips for distnguishing between exocrine and endocrine pancreas tissue?
Pancreas is 95% exocrine
Endocrine is mainly located in clusters of cells
Describe the structure of the pancreatic exocrine gland.
Secretory unit - pancreatic acini made of centroacinar cells
Channel into small intralobular (intercalated) ducts
Then large intralobular ducts
Then the interlobular duct
Then the main duct
Describe how the epithelial cell type changes along the pancreatic duct
Small intralobular (intercalated ducts) are simple sqaumous
Large intralobular are simple cuboidal
Interlobular are simple columnar
Main ducts are stratified columnar.
What type of duct will the pancreas be classified as?
compound acinar gland
What part of the pancrease duct is responsible for secreting HCO3?
Small intralobular or intercalated ducts
Made from simple cuboidal epithelium
What is the function of mineralcorticoids?
Stimulate renal absoprtion of water and sodium ions
Secretion of K+ ions
To maintain salt balance
(less important)
What is the function of glucocorticoids?
Influence carbohydrate matabolism
Suppress immune activites
What is the function of PP cells?
Are pancreatic endocrine cell
Secrete pancreatic polypeptide
Inhibits the secretion of pancreatic enzymes and HCO3-
What are the key endocrine cells in the parathyroid gland?
What do they do?
Chief cells
Secrete parathyroid hormone in response to low blood calcium
Stimulate osteoclast activity to move calcium ion from bone to blood
Also secrets calcitonin
What is the classification system of exocrine ducts?
Unicellular
Multicellular
Multicellular are then acini or tubule depending on their shape
Then compound or simple based on the configuration.
What is the key difference between an acinus and a duct?
Acinus is secretory portion
Duct is the conducting portion
Both are part of a exocrine gland
List the different types of simple glands
Simple tubular
Simple coiled tubular
Simple branches tubular
Simple alveolar (acinar)
Simple branched alveolar
List the different types of compound glands.
Compound tubular
Compound alveolar
Compound tubuloaveolar
What are the three different types of secretions and how are they different?
Merocrine - vescile release
Apopcrine - vesciel released within part of cell
Holocrine - vesciles are released within the entire cell
What are the two different types of duct systems that can be found in the salivary gland?
How are they different?
Serous acinus - watery secretion, inlcudes proteins such as digestive enzymes
Mucous acinus - thicker mucus secretion
What is meant by a mixed salivary gland?
What are their key features?
Contains both serous acinus and mucous acinus
Serous demilunes are often found ontop of mucous acinus
This is found in the submandibular and sublingual salivary glands
What is the function of myoepithelial cells related to glands?
Contract to release the secretion from the acini into the duct
How can you distnguish between serous acinus and mucous acinus cells in salivary glands?
Serous have a round basolaterally located nucleus
Mucuous acinus have a flat basally located nucleus, cells are typically white as filled with secretions.
What divies glands into lobes and lobules?
Connective tissue septa
What surrounds all glands?
A connective tissue capsule
Describe the organisation of salivary ducts
Mucus acinus and serous acinus make up the secretory portion
These will empty into intercalated ducts
Then into striated ducts
Then into interlobular ducts
Then into lobar ducts
What makes up the intralobular ducts of the slavary glands?
The intercalated ducts
The striated ducts
What is the cell type transition in the ducts of the salivary glands?
Intercalated ducts - simple squamous
Striated ducts - simple cuboidal
Interlobular ducts - simple columnar
Lobar duct - stratified columnar
What is the classification of the parotid salivary gland?
What are its key features?
Compund tubloacinar glands
Exclusively serous secretions
Has irregular collagenous connective tissue capsule and septa that divide into lobules
Serous cells secrete alpha amylase
Draw a diagram to show the histological representation of the thyroid gland
Identify the type of gland and it’s key features
Thyroid gland
Follicular cells are C
Colloid b
Blood vessel A
Stroma white area
Identify the gland and it’s key features
Pituitary gland
Posterior pituitary 1
Anterior pituitary 2
Pituitary stalk 3
Hypothalamus
Third ventricle
Optic chiasm
Identify the gland and it’s key features
Anterior pituitary gland darker
Posterior pituitary gland light
3 blood vessel
Capsule
What feature of the pituitary gland is highlighted by the arrow?
Herring bodies
Store hormone in the posterior pituitary gland before release
What are the features of the submandibular salivary glands?
Mixed ducts so serous, mucus and serous demilunes
opens onto floor of mouth
How can you distinguish between the medulla and the cortex of the adrenal gland?
Medullar is deep
Found after the darkest ring (which is the final zone of the cortex the zona reticularis)
Identify the features of the pancreas
1 endocrine islets of Langerhans
2 exocrine acinar cells
3 capsule
Label the key features of the pancreatic duct
1 pancreatic acini
Centroacinar cells
Small intralobular duct or intercalated duct
Large intralobular duct
Inter lobular duct
Main duct
Which salivary gland is this most likely taken from? Why?
Parotid salivary gland
Purely serous acini as only round nasally located nuclei
What salivary gland is this? Why?
What key features can you identify?
- Ducts
- Serous acini
- Connective tissue septa
Is a parotid gland, only serous acini shows as eosinophilic no large mucus white stained mucus acini
What salivary gland is this? Why?
What key features can you identify?
Submandibular or sublingual
1 striated duct
2. Mucous acini
3. Serous acini
4. Serous demilunes
What do ducts tend to look like under histological imaging?
Columnar cells ( larger than acini)
More white than acini
Central rounder located nucleus rather than a basal located nuclei
Tend to have a central lumen between cells.
Larger than acini
Label the sections if the salivary duct
1 serous or mucous acini
2 intercalated ducts
3 striated ducts
4 Inter lobular ducts
5 main duct
What are the different cell types of the different sections of the salivary ducts?
Intercalated ducts are simple squamous
Striated ducts are simple cuboidal
Inter lobular ducts are simple columnar
Lobular are stratified columnar
What are the different cell types of the pancreatic glands?
Small intralobular or intercalated are simple sqaoumous
Large intralobular are simple cuboidal
Inter lobular are simple columnar
Main ducts are striated columnar
What is the classification of the salivary ducts?
Compound tubuloalveolar ducts
What type of salivary gland is this?
What are the key features of it?
Submandibular salivary gland
Intercalated ducts
Mucous acini
Serous demilunes
Serous acini
Identify the different layers of the adrenal glands
Capsule
Zona glomerulosa
Zona fasciculada
Zona reticulada
Medulla
Cortex
Identify the key features of the pancreas
Inner pink area is the islet of Langerhans endocrine pancreas
Surrounding red area is the exocrine pancreas acini
How can you distinguish between the different cell types in the islet and Langerhans
Beta insulin’s producing cells stain blue!black
Alpha Glucagon producing cells stain red
When shown an islet of Langerhans what is a good way to distinguish between the alpha and beta cells?
Beta cells (insulin producing) make up the majority so will be in greater numbers
What is a sheet gland?
Many unicellular gland next to each other on an epithelial surface
E.g stomach mucus secreting
What are the features of a compound acinar gland?
Branching ducts in blue
Acini cells in the purple circle
Acini lumen in green arrow
Lobules in the oval
What are the features of a compound tubuloaveolar duct?
Have acini (purple sphere) and tubule (light purple) secretory units
Has lobules (blue spheres)
And branching ducts blue arrows
Identify the gland and the different ducts it contains
Parotid salivary gland
Identify the gland and the ducts it contain
Parotid gland
Striated and intercalated disk
