Download Histology Block Review – Part I

LYMPHATICS AND LYMPH NODES











Histology Block Review
How many liters out of the 20 liters of blood that circulates in the body each
day are filtered through the walls of capillaries in the form of an ultra filtrate
of plasma?
o 3 liters
When looking at a histological section, how can you tell the difference
between an Arteriole and a Lymphatic Capillary?
o Arterioles are more round, and they contain red blood cells.
o Lymphatic Capillaries have an irregular outline, and have a thinner
wall. They do NOT have red blood cells in them.
What do larger Lymph Vessels and Lymphatic Ducts have that Lymphatic
Capillaries do not have? Can you see these?
o They have VALVES
o They also have an Intima, Media, and Adventita
o You can see valves in the histological section
How can you tell that you are looking at Lymphoid Tissue (and not Lymph
Nodules)?
o Right under the Lamina Propria, you see a poorly outlined area of
Lymphoid Tissue, but no obvious organization.
Dr. Devan showed a slide of Lymphoid Tissue. What organ was this taken
from, and what do we call this type of Lymphoid Tissue based on the
location?
o Esophagus
o MALT – Mucosal Associated Lymphoid Tissue
Where would you find GALT?
o In the GI Tract – Gut Associated Lymphoid Tissue
Where would you find BALT?
o Bronchi of the lungs
o Broncus Associated Lymphoid Tissue
A histological slide of Secondary Nodules in the Appendix was shown. What
type of Lymphoid Tissue would this be characterized as?
o GALT (appendix is in the gut)
What are the two parts of a Secondary Lymph Nodule? What types of cells
are in each?
o Outer Portion – T-Lymphocytes
o Inner Portion (Germinal Center) – B-Lymphocytes
What is the difference between a Lymph Node and a Lymph Nodule?
o Lymph Nodes have a capsule around the outside, and Lymph Nodules
do not.
Through what Lymphatic Vessel does Lymph flow into the Lymph Node?
Where is this vessel located?
o Afferent Lymphatic Vessel
o Cortex

Though what Lymphatic Vessel does Lymph flow out of the Lymph Node?
Where is this vessel located?
o Efferent Lymphatic Vessel
o The Hilum
 What separates one Lymph Nodule from another in the Lymph Node (cortex
specifically)
o Trabeculae
 Besides the actual Nodules, where are most T-Lymphocytes located and
where are most B-Lymphocytes located?
o T-Lymphocytes – Cortex
o B-Lymphocytes – Medulla
 What do B-Lymphocytes mature into?
o Plasma Cells
 Is there blood flowing through the Lymph Node?
o NO!!!
o Blood is supplying the cells with nutrients, but the only thing filtered
through a Lymph Node is LYMPH.
 Dr. Devon showed a slide of the Subcapsular Sinus of the Lymph Node to
demonstrate the two types of cells found in this area. What are the two types
of cells, and how do you tell them apart?
o Reticular Cells – look empty
o Macrophages – Round cells dispersed throughout
 High Endothelial Venules are located in the Lymph Node. Why are they
important functionally?
o This is the site where the majority of T-Lymphocytes migrates out of
the vascular system and makes their way into the lymph node (90%)
 Does blood come through the HEVs?
o NO!!
 When the T-Lymphocytes migrate out of the HEVs, where do they go?
o To the Paracortex
 How can you tell a Lymph Node from the Spleen? How can you tell it from
the Lymph Nodule?
o A Lymph Node has a Subcapsular Sinus in pictures (Lymph Nodules
do not)
o A Lymph Node only filters Lymph, so it has no arteries running
through it (the Spleen does have arteries)
 What two structures are found in the medulla of the Lymph Node? What is in
them?
o Medullary Cords – Lymphocytes, Plasma Cells, Macrophages
o Medullary Sinus – Channels where the lymph flows through
 What type of simple epithelium do HEV’s have that sets it apart from other
veins?
o Cuboidal Epithelium (not squamous) – does NOT let blood out
_________________________________________________________________________________________________
SPLEEN










What is the main function of the Spleen?
o To filter BLOOD, to destroy old blood cells, to degrade hemoglobin,
etc.
How do you tell that a histological section of the Spleen is a Spleen and not a
Lymph Node?
o It has arterioles BETWEEN the GERMINAL CENTER and the TLYMPHOCYTES of the White Pulp. They are very difficult to see. Pay
attention. 
What is the White Pulp?
o The Splenic Nodules (with the Lymphocytes)
What is the Red Pulp?
o Where all of the blood drains around the White Pulp areas.
What is the path of blood into the Spleen?
o Splenic Artery  Trabecular Artery  Central Artery (PALS) 
Pennicilus Artery (Red Pulp)
What is a PALS?
o Periarterial Lymphoid Sheath
o A sheath of Lymphocytes surrounding the Central Artery
When the blood goes from the Penicillus Artery  Capillaries, it then goes
through a Splenic Sinus before leaving via veins. What are the Splenic
Sinuses called?
o Cords of Biliroth
What cells are filtering the blood when the Penicillus Artery dumps it into the
Red Pulp?
o Macrophages
Do humans have a Opened or Closed system?
o Open
What type of shape do Splenic Sinusoids have?
o Barrel shaped with arterioles wrapping around it.
_________________________________________________________________________________________________
THYMUS



What is the main function of the Thymus?
o Programming T-Lymphocytes that are produced in the Bone Marrow
What are the two general regions of the Thymus? (Microscopically)
o Cortex
o Medulla
What is the HUGE distinguishing feature to tell that you are looking at a
Thymus?
o In the Medulla, you see a bunch of Hassel’s Corpuscles. They look like
empty holes in the medulla region.




Does the Thymus have Afferent and Efferent channels?
o No – just Efferent
Which type of Endothelial Cell forms the Blood-Thymus Barrier?
o Endothelial Type 1
Is the Blood-Thymus Barrier in the Cortex or the Medulla?
o Cortex
How are cells “educated in the Thymus?”
o CFUs leaving the capillary in the Medulla and migrate to the Cortex.
o When they reach the Cortex, they display CD4 and CD8.
o Double Positive Selection: If you have CF4 and CD8, you pass and go
through the Blood-Thymus Barrier and into the Medulla
o In the Medulla, the cells lose either the CD4 or CD8 (and become the
cell that corresponds with the marker they kept)
o They are then presented with Self Antigen
o Negative Selection: If they still contain a Self Antigen on the surface,
they are killed.
o The rest are allowed into the blood.
_________________________________________________________________________________________________
PITUITARY GLAND









What type of tissue is the Anterior Lobe?
o Endocrine
What type of tissue the Posterior Lobe?
o Nervous
What is the Anterior Pituitary derived from?
o Rathke’s Pouch
What is the Posterior Pituitary derived from?
o Downgrowth of the Infundibulum (Diencephalon)
What are the three parts of the Anterior Pituitary?
o Pars Distalis
o Pars Intermedia
o Pars Tuberalis
Which part of the Anterior Pituitary contains remnants of the Rathke’s
Pouch?
o Pars Intermedia
What is the tissue called in the Posterior Pituitary?
o Pars Nervosa
What is the Blood Supply to the Pars Distalis?
o Internal Carotid  Two Superior Hypophyseal Arteries  Primary
Capillary Beds  Hypophyseal Portal Veins  Secondary Capillary
Bed
What is the Blood Supply to the Pars Nervosa?














o Inferior Hypophyseal Artery  Hypopphyseal Veins
What two releasing factors does the hypothalamus release, causing release at
the Pars Distalis?
o TSH
o RH
What two inhibitory factors does the hypothalamus release, causing
inhabitation at the Pars Distalis?
o Somatostatin
o Dopamine
What are the three types of cells found in the Pars Distalis?
o Acidophils
o Basophils
o Chromophobes
What do Acidophils produce?
o Growth Hormone
o Prolactin
What do Basophils produce?
o ACTH
o TSH
o FSH
o LH
What do Chromophobes produce?
o Nothing
How do you tell the difference between Acidophils. Basophils, and
Chromophobes in a Histological Section?
o Acidophils – reddish colored, medium in stain
o Basophils – blue colored, darkest in stain
o Chromophobes – do no stain
What are the relative percentages of these three cells?
o Acidophils – 40%
o Basophils – 10%
o Chromophobes – 50%
What two hormones are released by the Posterior Pituitary?
o ADH
o Oxytocin
Which hormone is produced by the Paraventricular Nuclei?
o Oxytocin
Which hormone is produced by the Supraoptic Nuclei?
o ADH
What lobe of the Pituitary do you find Herring Bodies?
o Posterior Pituitary
What are Herring Bodies?
o Collections of the ends of the axons that release neurotransmitters
What does the Pineal Gland produce?
o Melatonin



What is the function of the Pineal Gland?
o Circardian Rhythm
What are the two cell types and their functions?
o Pinealocytes – produce melatonin
o Glial Cells – support
What is the unique feature of the Pineal Gland that you use to identify it?
o Brain Sand (Corpora Arencaea)
_________________________________________________________________________________________________
ADRENAL GLAND














Where are the Adrenal Glands located?
o On top of the kidneys
What are the two areas of the Adrenal Gland?
o Medulla and Cortex
What does the Cortex secrete?
o Steroids
What does the Medulla secrete?
o Cathecolamines
What are the three layers in the Cortex?
o Zona Glomerulosa
o Zona Fasciculata
o Zona Reticularis
What is the main factor  hormone secreted in the Zona Glomerulosa?
o Angiotensin II  Aldosterone
What is the main factor  hormone secreted in the Zona Fasciculata?
o ACTH  Cortisol
What is the main factor  hormone secreted in the Zona Reticularis?
o ACTH  Androgens
What cell type is unique in the Medulla of the Andrenal Gland?
o Chromaffin Cells
What are the two blood supplies of the Adrenal Gland?
o Medullary Arteriole  straight to the medulla
o Adrenocortical/Adrenomedullary  Capillaries  Sinusoids
What does the Adrenal Gland secrete?
o Epinephrine
o Norepinephrine
DUAL INFLUENCE ON ADRENAL FROM NERVOUS SYSTEM AND HORMONES
What is one way to distinguish Adrenal Gland on a histological slide that is at
a high power?
o A bunch of fat droplets are in it.
What are Chromaffin cells?
o Neuroendocrine cells (modified neurons)
_________________________________________________________________________________________________
THYROID/PARATHYROID GLAND













What is the function of the Thyroid Gland?
o To control the metabolism of cells
What is unique about the Thyroid Gland?
o It is the only one that stores its product
How do you recognize it in a histological section?
o You see large storage areas surrounded by a bunch of follicular cells
What does the Thyroid produce?
o Calcitonin
In the large storage areas, there are empty white spots. What is this?
o Where the product stored inside has been taken up by the cells
What do Parafollicular Cells produce?
o Calcitonin
What is Calcitonin antagonistic to?
o Parathyroid Hormone (PTH)
What two molecules need to come into the cell so that it can begin to form T3
and T4?
o Iodide
o Thyroglobulin
T3 and T4 are stored by being combined with what?
o Iodine
What is the function of the Parathyroid Gland?
o Regulate Calcium and Phosphate levels
What are the two cell types in the Parathyroid Gland?
o Chief Cells
o Oxyphil Cells
What is the function of these cells?
o BOTH produce Parathyroid Hormones
How do you tell the difference between Chief Cells and Oxyphil Cells?
o Oxyphil cells stain darker and look like fried eggs
_________________________________________________________________________________________________
PANCREAS



What are the cell islands in the Pancreas called? Where are they mainly
located?
o Islets of Langerhans in the Pancreas
What two cells are located in the pancreas? What do they produce?
o Alpha Cells – Glucagon
o Beta Cells – Insulin
What do D-Cells produce?

o Somatostatin to inhibit Alpha and Beta Cells
What do F cells produce?
o Pancreatic Polypeptide
_________________________________________________________________________________________________
LIVER








What are some functions of the liver?
o Detoxify the blood
o Produce bile
o Synthesize lipids
What do you look for when identifying the liver?
o Portal Triads between each unit with a Central Vein
There are 3 concepts of Hepatic Organization. Given each one, describe what
it means:
o Classic Lobule
 Blood Organ – making hormones and putting them into the
Central Vein
o Portal Lobule
 From the Central Vein towards the Bile Duct
o Liver Acinus
 Cells that are furthest from oxygen are at risk
What is unique about the cells around the bile duct?
o They are more cuboidal and usually darker than arterioles
What is an Ito cell?
o Vitamin K Storage
What are Kupffer Cells?
o Macrophages
What is the Canal of Herring?
o Important because it has stem cells in it.
What is the Space of Disse?
o The space that is lined with endothelial cells containing microvilli for
absorption
_________________________________________________________________________________________________
GALL BLADDER

What is the function?
o To store bile
_________________________________________________________________________________________________
SALIVARY GLANDS





What type of secretion does the Partoid Gland secrete?
o Serous
What type of secretion does the Lingual Gland secrete?
o Mucus
What type of secretion does the Submandibular Gland secrete?
o Mixed
How can you tell the difference between a Intercalated and a Striated Duct?
o The striated one has lines on it
How do you know when you are looking at the exocrine part of the Pancreas?
o Acinar glands are present but you see NO striated ducts
_________________________________________________________________________________________________
THE TONGUE



What are the four types of Papillae?
o Circumvallate
o Foliate
o Fungiform
o Filiform
Which Papillae has Ebner’s Glands?
o Circumvallate Papilla
Which Papillae lack taste buds?
o Filiform Papillae