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x. Histology Test III > Circulatory System > Flashcards

Circulatory System Flashcards

1
Q

3 major components of the circulatory system

A

Divided into 3 major components:

  1. Blood vascular system
  2. Lymphatic system = returns tissue fluid back to the bloodstream
  3. Hemopoietic Organs/Tissues = blood cell producing structures
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2
Q

Circulation of blood in tetrapods

A
  1. Heart pumps blood to (a) lungs for oxygenation (pulmonary circulation - right side) and (b) the rest of the body (systemic circulation - left side).
  2. Arteries take oxygenated blood from heart to rest of body, branch to become smaller distally.
  3. Capillaries are small thin-walled vessels, generally receive blood from arteries, empty to veins

Gas and nutrient exchange occur across walls.

  1. Veins return blood from the tissues to the heart, merge to become larger as they approach heart.
    In some cases, veins supply a second capillary bed = portal system
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3
Q

Describe the basic cross-sectional structure of a blood vessel

A

Inside to outside orientation:

  1. Tunica Intima (interna) = consists of simple squamous endothelium + subendothelial CT (areolar with reticular fibers) + internal elastic membrane
  2. Tunica Media = composed of concentric layers of smooth muscle (cardiac muscle in aorta as it exits heart) and fenestrated elastic membranes. Some small vessels may lack this layer.
  3. Tunica Adventitia = consists of outer elastic membrane (ill-defined) surrounded by lamellated CT. Contains blood vessels in larger arteries and veins (vasa vasorum).
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4
Q

Describe the categorization of arteries.

A

Customarily divided into 3 groups, but actually get continuous reduction in size away from heart.

Large Elastic Arteries

Muscular Arteries (small to medium-sized)

Arterioles

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5
Q

Muscular artery

A

relatively thick tunica media, lumen relatively small and oval/round.

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6
Q

arterioles

A

everything reduced, stress is less therefore less elasticity necessary

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7
Q

elastic arteries

A

large increase in elastic tissue in walls since have high stress due to high blood pressure

forms flat sheets of fibers with pores (= fenestrated membranes)

really thick, think of the aorta

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8
Q

Vein categorization

A

Also customarily divided into 3 groups
Sinus = expansion of veins, covers wide area
Medium-sized Veins
Venules

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9
Q

Medium vein

A

thinner-walled than artery; lumen larger and usually oblong

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10
Q

venules

A

everything is reduced

thin T. adventitia, may lack tunica media

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11
Q

large vein/sinus

A

tunica media is virtually pure smooth muscle
very little CT
T adventitia is proportionately thicker

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12
Q

Artery/vein comparison

A

Artery:
Lumen is 1/2 wall thickness and oval
Maintains rigidity
inner elastic membrane is heavy

Vein:
lumen larger, relative to wall, oblong.
collapses without blood
inner elastic membrane is slight and not distinct.

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13
Q

General info about capillaries: size of capillaries? What are they made of?

A

lumen: 8-10 um
up to 30 um

thin walled vessels

Walls consist of endothelium + basal lamina+ thin sheath of delicate collagen and reticular fibers in larger capillaries

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14
Q

What are the 3 types of capillaries

A

continuous
fenestrated
sinusoidal

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15
Q

continuous capillaries

A

endothelial cells provide uninterrupted lining with well-developed basal lamina

Tight junctions don’t extend all around periphery, allows passage of small molecules.

Found in lung, muscle, skin, etc.

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16
Q

fenestrated capillaries

A

endothelial cell cytoplasm contains pores, closed by a thin diaphragm except in glomerulus of kidney

Diaphragm formed by fibrils that radiate toward pore center but leave small (5-6 nm) wedge-shaped channels

Found in intestinal mucosa, endocrine glands, glomerulus

INCREASE EXCHANGE OF DISSOLVED THINGS

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17
Q

Sinusoidal capillaries

A

arger lumen; irregular walls with wide gaps between endothelial cells

Found in liver, bone marrow, spleen

PROMOTES CELLULAR EXCHANGE

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18
Q

What makes up the lymphatic system

A

lymphatics and lymph nodes

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19
Q

lymph vessels

A

look like small to medium-sized veins without RBCs

tunics somewhat less distinct

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20
Q

Lymph capillaries

A

resemble continuous capillaries but:

Basal lamina is incomplete or lacking

One end terminates blindly, fluids enter via diffusion + some hydrostatic pressure

Generally larger lumens

Anchoring filaments extend from outer surface into surrounding CT to hold vessels open

21
Q

Lymph vessel valves

A

Lymph vessels with valves to prevent backflow in amniotes. Lymph movement is facilitated by skeletal muscle contraction.

Lymph hearts propel lymph in amphibians and to a lesser extent in reptiles.

22
Q

Myeloid tissue

A

red bone marrow

active bone marrow; present in cavities of sternum, ribs, vertebrae, skull, proximal ends of some long bones

23
Q

Components of myeloid tissue

A

Stroma = vascular CT supported by a network of collagen and reticular fibers. Also present are phagocytic reticular cells and singular adipose cells.

Developing Blood Cells = many types and stages present

Sinusoids = associated with outer surface are phagocytic reticular cells; newly formed blood cells gain access to circulation by passing through sinusoid wall

24
Q

Inactive bone marrow

A

Yellow Bone Marrow = most of hemopoietic tissue replaced by adipose.

Under certain conditions, yellow marrow may be converted to active state → undifferentiated mesenchyme cells proliferate and form myeloid cells.

25
Q

Function of lymphoid tissue

A

Lymphoid Tissue = basic feature is heavy population of lymphocytes; functions in defense against infection and in immune response

26
Q

Types of lymphocytes, sites of differentiation, function.

A

2 Types of Lymphocytes; differ in cell surface proteins

T-lymphocytes = differentiate in Thymus; responsible for cell-mediated immune response; 4 subtypes with differing functions (cytotoxic, helper, memory, suppressor)

B-lymphocytes = differentiate in red bone marrow; responsible for humoral antibody response

27
Q

What is the thymus?

A

site of T-cell differentiation, located near base of neck.

Gross structure: bilobed, subdivided into 1000s of lobules.

28
Q

Describe a thymus lobule

A

Each lobe enclosed in CT capsule with inward extensions (trabeculae)

Each lobule divided into outer cortex (where lymphocyte production takes place) and inner medulla (less numerous lymphocytes and therefore pale-staining;

presence of Hassal’s Corpuscles

29
Q

What are Hassal’s corpuscles?

A

spherical eosinophilic structures formed by concentrically arranged reticular epithelial cells with marked tendency to keratinize)

30
Q

Three elements of thymic morphology

A

epithelial element: extensive loose network of epithelial reticular cells (=stellate cells with pale-staining nuclei)

lymphatic element: T-lymphocytes at various developmental stages

connective tissue element: capsule + trabeculae of collagen

31
Q

Are there afferent lymph vessels?

A

No afferent (incoming) lymphatic vessels in thymus, lymphocytes enter bloodstream via thin-walled venules or efferent lymph vessels present in trabeculae.

32
Q

Lymph nodules

A

spherical aggregations of lymphocytes in loose CT underlying digestive, respiratory and urinary epithelium

they’re unencapsulated, most are small and solitary

structurally, may show pale center where lymphocytes are actively enlarging and dividing = germinal centers

nodules act as first line of defense against microorganisms passing through leaks in epithelium

33
Q

Where are lymph nodules usually found

A

in areas open to the outside.. first line of defense

34
Q

What do we call sites where lymph nodules are large and multiple?

A

tonsils

35
Q

What are tonsils? Name 3 of them.

A

unencapsulated aggregates of lymphoid tissue forming incomplete ring circling entrance to digestive and respiratory tract

Palatine = posterior roof of mouth

Lingual = base of tongue

Pharyngeal = surrounding posterior nasopharynx

36
Q

Peyer’s patches

A

aggregates in wall of ileum (lymph tissue)

37
Q

Appendix

A

large lymph nodules in wall for immune function

38
Q

Describe lymph nodes

A

only found in mammals, encapsulated kidney-shaped structures occurring as enlargements along lymph vessels

39
Q

Structural elements of lymph nodes

A

Capsule = CT with inward extending trabeculae

Cortex = outer portion, contains nodules

Medulla = inner portion, branching lymphoid strands (lymph cords) enclosing a number of open lymph spaces (medullary sinuses)

40
Q

How does lymph enter lymph nodes?

A

Lymph enters via afferent vessels on convex side of node; exits via efferent vessels at hilum (“dent” in kidney)

41
Q

What’s the function of a lymph node?

A

Proliferation of B-cells during immune response

Recirculation of lymphocytes after phagocytic removal of degenerating cells and particulate matter = filtering function

42
Q

What is the spleen?

A

Large elongate organ in abdominal cavity; lies across blood circulation to act as “blood filter,” as lymph node acted as lymph filter.

43
Q

What are the structural elements of the spleen?

A

CT Capsule = covered by mesothelium, trabeculae extend inwardly; made up of dense collagen fibers + elastic fibers + some smooth muscle

Red Pulp =

White Pulp =

44
Q

What is the red pulp?

A

spleen part

majority of internal spleen is this; composed of (i) numerous wide thin- walled sinusoids, and (ii) supporting network of reticular cells and fibers with numerous free RBCs, macrophages present

45
Q

what is the white pulp?

A

typical lymphatic tissue (B-cells mainly) surrounding and following arteries, forms pale islands of tissue (= splenic nodules)

46
Q

Where do arteries and veins enter/exit the spleen?

A

hilum

47
Q

Functions of the white pulp and red pulp of the spleen

A

White Pulp

Antibody production via proliferation of B-cells in white pulp

Red Pulp

Disposal of defective blood cells, especially RBCs
Storage of RBCs, when needed releases RBCs into circulation

48
Q

Discuss the argument about open/closed circulation of the spleen.

A

Not completely known – both likely occur.

Open = terminal arterial capillaries open into pulp reticulum and blood gradually filters into venous capillaries (sinusoids)

Closed = arterial capillaries enter directly into venous sinuses, but capillaries with large holes (discontinuous capillaries) so RBCs can be exchanged freely

It appears that open circulation predominates and that closed circulation serves only a minor role.

x. Histology Test III (8 decks)

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