Semester II, Weeks 1-3 (Vessels, Lymph, Mouth) Flashcards by Dustin O

What tissue is this?

How can you tell?

What are the labeled layers?

Elastic Artery

tunica media has many parallel elastic fibers called fenestrated elastic membranes throughout, with “fishbone” oriented smooth muscle nuclei visible between them
arrow - tunica intima
M - tunica media
A - tunica adventitia

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If a lumen is visible within the tunica adventitia of a large artery, what is it?

vasa vasorum

(literally “vessels of vessels”)

small vessels that supply blood to the outer layers of the larger vessel

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What are the 3 layers of a blood vessel, from innermost to outermost, and what do they contain?

tunica intima - endothelium (SSE) + subendothelial loose CT layer
tunica media - smooth muscles cells, elastic fibers
tunica adventitia - loose CT, nerve fibers, vasa vasorum

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How does the tunica media differ between elastic and muscular arteries?

elastic - **fenestrated elastic membranes **evenly distributed throughout entire tunica media, with “fishbone” oriented smooth muscle nuclei between elastic fiber layers

muscular - tunica media is surrounded by **internal and external elastic laminae **and contains only smooth muscle, without elastic fibers

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What is the predominant layer in arteries vs. veins?

arteries - tunica media predominates

veins - tunica adventitia predominates

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What is this tissue?

Name the labeled parts.

What layer is the arrow part of?

How are the circled V lumen and the circled A lumen differentiated?

Muscular Artery and Vein

A - adventitia, M - media

circled V - venous lumen, circled A - arterial lumen

arrow - internal elastic lamina (part of intima)

venous lumens are larger and more “squashed” in shape than the smaller, more circular arterial lumens

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What are the small granules within endothelial cells called?

What do they contain?

Weibel-Palade Bodies

contain von Willebrand Factor and P-selectin for clotting and inflammatory purposes, respectively

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What is the central structure here with a lumen?

How can you tell?

How many layers of cells typically surround its lumen?

Arteriole

small, round lumen and thick wall with less than 5 cell layers

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What structure is shown here with its lumen indicated by the arrow?

How can you tell?

Venule

large, amorphous lumen with very thin wall

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How can capillaries be identified on slides?

What 3 types of capillaries are there?

capillaries are extremely small, with a lumen of about 7-9 µm just big enough for 1 RBC
a capillary wall’s cross-section is made up of just 1-3 endothelial cells

Types:

continuous
fenestrated
sinusoid

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What is this tissue?

How can you tell?

What are the labeled structures?

Palatine Tonsil

lymphatic follicles indicate a tonsil, deep crypts and a capsule indicate palatine

C - crypt. arrow - capsule, circle arrow - SSNKE lining crypts

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What kind of tissue is shown here?

How can you tell?

What are the labeled structures?

What is at the center of structure F?

Tonsil Tissue

(structures shown do not allow differentiation between palatine, lingual, etc.)

follicles below stratified squamous epithelium indicate tonsils

F - follicle with germinative center

arrow - infiltration of epithelium by lymphocytes

arrow with circle - SSNKE

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What is the name for the category of tissue that tonsils and the appendix are in?

MALT

Mucosa Associated Lymph Tissue

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What kind of cells make up lymphatic follicles?

**lymphoblasts **in the germinative center with **B lymphocytes **around the edges

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What kind of cells surround the follicles?

And what are these areas called (2 possible terms)?

T-Lymphocytes

**Interfollicular Areas **or T-Dependent Zones

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This is not an ideal picture, but…

What is the tissue?

How can you tell?

What are the labeled structures?

Lingual Tonsil

crypts and follicles indicate a tonsil;

glands, fat and muscle indicate lingual

F - follicle, C - crypt, D - excretory duct, G - salivary gland

arrow - SSNKE, circle arrow - lymphatic infiltration

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What are the main differences between the lingual and palatine tonsil slides?

lingual

shallow, wide crypts
visible skeletal muscle, mucous acini, adipose tissue

palatine

deep, narrow, branching crypts
surrounded by capsule

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What is this organ?

How can you tell?

What surrounds the organ? (not easily seen here)

And what continuations of that surrounding enter into the organ itself?

Lymph Node

darker outer cortex and lighter inner medulla is characteristic of the lymph node
CT capsule surrounds the organ and CT trabecules continue from the capsule into the node

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What is the darker outer layer of this organ (left) and what is it made up of?

What are the branchings (not clearly visible here) of the darker tissue into the lighter area on the right called?

Cortex w/ lymphatic follicles
Medullary Cords made up of plasma cells, macrophages and B-lymphocytes extend from the cortex into medulla

What is the area between the darker outer and lighter inner parts of this organ called?

What does it contain?

Paracortex - between cortex and medulla of lymph node

contains T Lymphocytes

What is the area between the capsule and cortex of this organ called (not clearly visible here)?

What similar areas is it continuous with?

What is in them and what purpose do they serve?

Marginal Sinus lies between capsule and cortex, allows inflow of fluid from afferent vessels…

It’s continuous with Intermediate Sinuses along trabeculae and Medullary Sinuses within the medulla…

They contain reticular cells, fibroblasts and histiocytes (fixed macrophages)

What vessels serve and drain this organ?

Where do they enter/exit?

multiple Afferent Lymph Vessels flow into the node around the cortical edge

one Efferent Lymph Vessel flows out from the hilum where an artery/vein also supply/drain the node

What special vessels allow lymphocytes to enter lymph nodes from the blood?

Where in the node do they enter?

And how do they re-enter the blood when leaving the node?

High Endothelial Venules - post-capillary vessels with cuboidal endothelium

drain lymphocytes into paracortex
lymphocytes exit nodes via the efferent lymph vessels > thoracic duct > angulus venosus > blood circulation

What is this organ?

How can you tell?

Spleen

has lymph follicles and a capsule
does not have distinct cortex/medulla structure as in nodes
does not have pits, muscle and adipose tissue as in tonsils

1. What are the distinct darker purple areas... not just the follicles but all the darker purple parts of this organ? 2. And what two kinds of structures make up the purple areas? 3. And the lighter pink areas? 4. And what two kinds of structures make up the pink areas?

1. **_White Pulp_** - about 20% of spleen * **_PALS_** (peri-arteriolar lymph sheath) * **_Malpightmian Follicles_** (splenic lymphatic follicles) 2. **_Red Pulp_** - about 80% of spleen * **_Sinusoids_** * **_Billroth's Pulp Cords_** (surround sinusoids)

What is the light round structure in the center of this image? And the darker area surrounding it?

**Central Arteriole** surrounded by **PALS** (peri-arteriolar lymphoid sheath)

How can one differentiate between a Malpighian follicle and a central arteriole w/ PALS in cross-section?

Malpighian follicles have obvious, lighter germinative centers PALS has no germinative center the only lighter central tissue is the arteriolar wall and lumen

What is the difference in cell types between the two white pulp structures of the spleen?

**Malpighian Follicles** are "B Dependent" **PALS** is "T Dependent"

What are these lighter areas? What external structure are they continuous with? What runs through them?

**Splenic Trabeculae** - continuous with the CT **capsule** of the spleen - **trabecular arteries** **and veins** run through them

What are the empty-looking spaces in the spleen called? What are the cells that surround them and how are they distinguishable from endothelium? What is the purpose of this system?

**splenic sinusoids** surrounded by **stave cells** whose **nuclei bulge into the lumen** of the sinusoid - sinusoids receive RBCs from Billroth pulp cords through gaps between stave cells in order to filter out old, inflexible cells

What is this organ? How can you tell?

**Spleen** - same structures as in other slide but this is the washed specimen without blood

What structures are more visible in this slide than the other slide of the same organ?

- **reticular fibers** can be seen in the red pulp areas - **PALS** and **Malpighian** follicles stand out from the surrounding red pulp areas more

What is the route of blood into and out of the spleen?

1. **Splenic Artery** 2. **Trabecular Artery** (through CT trabecules) 3. **Central Arteriole** (surrounded by PALS) 4. **Pencillar Arteries** (branch off central arterioles) 5. **Billroth's Pulp Cords** (carry RBCs to sinuses) 6. **Stave Cells** (filter old RBCs) 7. **Sinusoids** 8. **Pulp Vein** 9. **Trabecular Vein** 10. **Splenic Vein**

What structure in the spleen is responsible for removing large antigens from the blood?

**Schweigger-Seidel Sheath** - macrophages + plasma cells around **ellipsoid** sheathed capillaries which phagocytize antigens

What is this organ? How can you tell?

**thymus** - distinct lobules

What is this cell? How can you tell?

**Epithelioreticular Cell** - found throughout cortex + medulla of thymus - ensure that T-lymphocytes are not auto-immune - lighter staining round cells amongst thymocytes ... at this magnification it is clear that this is the thymus because a Hassall body can be seen easily at the bottom of the picture

What are these structures?

**Hassall's Corpuscles** - made up of degenerated epithelioreticular cells - uncertain function but produce interleukins and contain keratohyalin granules

What does the arrow indicate (2 names) ? How can you tell?

**Vermilion Border** or **Rubor Labii** - transition between **mucosal** and **cutaneous** parts of lip - hair follicles are visible around the bottom edge of the specimen and labial glands are visible at the top left

What is the slightly darker purple area just below the pointer?

**labial glands** - seromucus glands opening into the oral vestibule

What is the blue circled area here?

**skeletal muscle** - in the lip, shown here in cross section

What are the jagged outcroppings of tissue at the top of this slide? How can you tell?

**Filiform Papillae** - most common tongue papillae - cover most of front 2/3 of tongue - **skeletal muscle** is visible below, indicating the tongue, and the characteristic **forkedness** of the filiform papillae can be seen

What is the layer just below the pointer but above the darker pink staining area?

**aponeurosis linguae** - aponeurosis of the tongue just below the lamina propria mucosae and above the skeletal muscle

What is the large, bulbous structure in the middle of this image? Where are they found?

**Fungiform Papilla** - found among the filiform papillae, but mostly on the tip and sides of the tongue - contain taste buds

What is the structure indicated by the pointer? How can it be distinguished from others like it? Where is it found?

**Circumvallate Papilla** - sits in a **deep cleft** and is the **largest type** of papilla - found along the terminal sulcus between the **papillary** and **follicular part** of the tongue - contains taste buds (seen below)

What is the circled structure? How do you know? What does it do?

**Ebner's Glands** - because it is just below the cleft of a circumvallate papilla - secretes **lingual lipase** to begin lipid hydrolysis in the oral cavity - also washes off surfaces of taste buds so they can receive new stimuli

What are the circled structures? How can you tell?

**Taste Buds** - they are round, lighter staining multi-cellular structures just deep to the surface of a circumvallate papilla