Cardio microanatomy (lectures 1 and 2)

structure of vessel wall

vessels larger than capillaries have 3 concentric layers, intima, media, and externa

tunica interna

endothelium and its BM with small amount of underlying CT, internal elaxtic membrane, has gaps to allow for communication of endothelium

tunica media

smooth muscle arranged in curcular patter, thickness varies, has collagen fibers and related CT matrix, may have elastic laminae, external elastic membrane seen in larger vessels

tunica externa

type 1 collagen and elastic fivers, blends into surrounding CT, has small nerves and vessels, may contain smooth muscle

elastic vessels

conduits for moving large volumes of fluid, tunica media is modified to contain many layers of fenestrated elastic laminae, making these arteries “stretchy”, maintains even flow and constant bp between heart beats

muscular vessels

axillary and femoral arteries, walls will contract and expand to distribute blood, tunica media is modified to contain many layers of smooth muscle, regulate volume delivery in response to peripheral demand

arterioles

resistance vessels, tunica interna present with thin internal elastic membrane, smallest arteries with reduced layers of smooth muscle, controls distribution of blood to capillaries through vasoconstriction and dilation

capillaries

are endothelial tubes that consist of endothelium and BM, no tunica media, 3 basic types (continuous, fenestrated, sinusoidal)

lymphatic capillaries

very irregular shape, have valves, appear similar to venules but should have proteinaceous lymph fluid residue in the lumen

venules

post-capillariy in position, similar in size to capillaries but larger in diameter, thin tunica media

small to medium veins

constitute most of the anatomically named veins, smooth muscle in tunica media, but always less than in companion artery, collagen and elastic fibers in adventtia

large veins

may have internal elastic membrane, less smooth muscle than companion artery

endocardium

inner layer of heart, continuous with the tunica intima of vessels, comprised of endothelial lining and subendothelial CT, heart valves are endocardial folds

myocardium

middle layer and thickest layer, continuous with tunica media of vessels, cardiac muscle, CT, and purkinje cells and fibers

epicardium

pericardium, outer layer, continuous with the tunica externa of vessels, serous membrane

what is number 1?

atrium

what is number 2?

ventricle

what is number 3?

coronary vessels (artery on right and vein on left)

what is number 4?

atrioventricular valve (AV)

what is number 5?

epicardium/pericardium

what term do we use when referencing simple squamous epithelium lining the outer surface of the heart?

mesothelium

what is 6a and 6b?

endocardium/endothelium

what part of the heart is 6b?

ventricle

what kind of fibers are in the ventricle?

purkinje

is this a muscular or elastic artery?

muscular

what is number 1?

tunica interna

what is number 2?

tunica media

what is number 3?

tunica externa

what is the pink line running through the tunica interna?

internal elastic membrane

is this vessel a muscular artery or an elastic artery?

elastic

is this elastic or muscular artery?

elastic

what is 1?

artery

what is 2?

vein

what is 3?

lymphatic vessel

what is 1?

vein

what is 2?

artery

what is 3?

lymphatic vessel

what are the yellow arrows pointing at?

capillaries

hilus

indentation where blood vessels enter and exit the node, and where efferent lymphatic vessels exit

parts of stroma

capsule, trebeculae, reticular CT network

capsule

dense irregular CT

trabeculae

continuous with the capsule, penetrate the parenchyma, may contain smooth muscle

reticular CT network

reticular cells and their secreted fibers (type 2 collagen), supportive scaffolding for lymphocytes

modular cortex

mostly B-lymphocytes, have primary and secondary follicles

primary follicle (nodule)

low level of any mitotic activity, unstimulated or resting condition

secondary follicle

high level of mitotic activity, centrally located germinal center surrounded by mantle

germinal center of secondary follicle

clonally dividing B lymphocytes

mantle of secondary follicle

non-proliferating B lymphocytes

diffuse paracortex

diffuse lymphoid tissue, surrounds cortical follicles and separates cortex fromm medulla, lymphocytes found in region are mostly T cells, venules, HEV

HEV

high endothelial venules, where lymphocytes exit the blood circulatory system and enter the paracortex

medulla

divided into the medullary cords and sinuses

medullary cords

rich in plasma cells, T and B lymphocytes and macrophages

medullary sinuses

part of sinus system of the lymph node

sinuses of lymph node

channels through which lymph fluid flows, less densely populated with lymphocytes, reticular cells form structural scaffolding, lymph fluid flows

subscapular sinuses

less cellular spaces deep to the capsule

cortical sinuses

less cellular spaces within diffuse paracortex that tend to be around trabeculae, connect the subscapular to medullary

medullary sinuses

less cellular spaces within the medulla, drain the different lymphatic vessel at the hilus of node

lymph flow in node

1. lymph enters from afferent lymphatic

2. flows through subscapular sinus

3. flows through cortical sinus

4. flows through medullary sinus

5. flows out of node through efferent lymphatics at hilus

spleen

largest of lymphoid organs, only organ specialized in filtering blood

hilus of spleen

long indentation where splenic blood vessels enter and exit

capsule of spleen stroma

dense irregular CT, varying amount of smooth muscle

trabeculae of spleen stroma

continuous wit hthe capsule, trabecular artery here, varying amount of smooth muscle

reticular CT network of spleen stroma

reticular cells and their secreted fibers (type 3 collagen), supportive scaffolding for red and white pulp

white pulp

refers to both diffuse and nodular lymphoid tissue, periarterial lymphatic sheath and splenic follicles

periarterial lymphatic sheath (PALS)

diffuse lymphoid tissue surrounding central arteries, mainly T cells but can include APCs (macrophage and dendritic)

splenic follicles

lymphatic follicles, dense accumulation aggregates of B-cells located in margins of PALS, may have germinal centers, and receive blood from branches of central artery (nodular artery)

red pulp

splenic sinuses and cords

splenic sinuses

lined by endothelium with discontinuous BM, RBCs must be flexible enough to pass from cords into sinuses, if inflexible become trapped and are phagocytized by macrophages which recycle iron from hemeglobin

splenic cords

located between splenic sinuses, highly cellular, contain macrophages filled with hemosiderin deposits

hemosiderin deposits

storage form of iron derived from the breakdown of red blood cells

marginal zone

located between red and white pulp, important site for antigen trapping

sequence of flow in spleen

1. splenic artery

2. trabecular artery

3. central artery

4. various arterioles

5. capillaries

6. splenic cords or sinuses

7. trabecular veins

8. splenic veins

function of spleen

immunological defense via filtration of blood for detection of pathogens, temporary storage of RBCs, removal of old RBCs by macrophages and recycle iron

MALT

mucosal associated lymphoid tissue, common in most mucous membranes, tonsils, BALTs GALTs,

tonsils

aggregates of lymphoid tissue nodules in the pharynx

palantine tonsil

mucosa of oropharynx, lined by stratified squamous epithelium, composed of both diffuse and nodular lymphoid tissue

tonsillar crypts

some species have theirs, indentations of epithelium into lymphoid tissue to increase surface area

BALT

bronchus associated lymphoid tissue, aggregates of nodular and diffuse lymphoid tissue in the bronchi and bronchioles

GALT

gut associated lymphoid tissues, diffuse and nodular lymphoid tissue in GI tube

peyers patches

lymphoid tissue found in lamina propria of small intestine

what type of immune organ is this?

lymph node, secondary lymphoid organ

what part of the lymph node is 1?

medulla

what part of lymph node is 2?

cortex

what are the yellow arrows pointing to?

capsule

what are the blue arrows pointing to?

trabeculae

what is the yellow circle?

subscapular sinus

what is the green circle?

cortical sinus

what CT is encircled in yellow?

dense irregular

what is the scaffold-forming cell encircled in green?

reticular cell

what is the cortical structure encircled in orange?

follicle/nodule

what is 1

medullary sinus

what is 2?

medullary cords

what is 3?

blood vessel

what is indicated by the X

germinal centers

what are the arrows pointing at?

mantles

what lymphocyte type is mainly in the orange circle?

B cells concentrated in the nodules

what lymphocytes are in the green circle

T cells, concentrated in the diffuse paracortex

what structure is indicated by the black circle?

white pulp

what structure is indicated by the orange X?

red pulp