Cardio System

Question 0

Weibel-Palade bodies, what is it?

Answer 0

• Contain clotting factor VII aka von Willebrand factor
• present in heart endothelium, elastic arteries, medium or muscular arteries, small arteries & arterioles but NOT IN CAPILLARIES
• Absence of W-P bodies can cause cutaneous & mucosal bleeding including menorrhagia

Question 1

ACE, where is it produced and what’s its fx?

Answer 1

Endothelial cells contain ACE, which facilitate conversion of ATI & ATII (especially in lung capillaries) -> vasoconstriction -> increased BP

Question 2

Elastic or Large Arteries fx?

Answer 2

• Conducting
• Ex. Aorta & main branches
• large number of elastic sheets or laminae in tunica media (40-70 laminae, smooth m. cells, type III collagen)
• Elastic laminae are arranged concentrically with interconnecting elastic fibre networks
• Structural significance: expansion of vessel wall to accomodate the large volume of blood during systole
• Elastic recoiling to maintain intravascular pressure
• Tunica adventitia: Type III & I collagen, elastic fibres, fibroblasts and macrophages

Question 3

Muscular or medium arteries fx?

Answer 3

• Distributing
• most abundant in body
• contain more smooth muscles in tunica media than elastic fibres
• IEL is strongly characteristic of muscular arteries
• Significance: serve as a muscular conduit to distribute blood to specific organs and muscles from large, elastic arteries to smaller arteries
• Tunica media: 8 to 40 layers of smooth muscle cells arranged in circular fashion

Question 4

Small artery features?

Answer 4

• No vasa vasorum

- T. Media: 3 to 8 layers of smooth muscle cells, arranged in apparent circular fashion

Question 5

Arterioles features? Very high yield

Answer 5

• Major determinants of BP
• T. Media: 1 or 2 layers of smooth muscle cells
• T. Adventitia: ill-defined, it merges with surrounding CT
• Architecture in parallel; blockage can lead to series architecture

Question 6

Capillaries features?

Answer 6

• single layer of endothelial cells + basal lamina
• may be encircled by pericytes (derived from mesenchymal cells; can squeeze capillary) in continuous capillaries
• 3 types of capillaries:
  1. Continuous (or classic) capillary: complete control over diffusion & transcytotic processes; pinocytotic & exocytotic vesicles, including receptor mediated endocytosis
  2. Fenestrated capillary: with diaphragms or/and circular pores; often found in peptide-secreting endocrine organs and kidney glomerulus, gut capillaries; continuous basal lamina; tight junctions present b/w cells; eye cillary processes, choroid plexus
  3. Discontinuous or Sinusoidal capillary: perforations large and variable; sites liver and some lymphoid organs (bone marrow, spleen, lymph nodes)

Question 7

High Endothelial Venules (HEV) significance?

Answer 7

Homing effect in lymphoid organs like lymph node

Question 8

Large vein features?

Answer 8

• T. intima: subendothelial layer with few smooth muscles
• T. media circularly arranged smooth muscles + CT
• T. Adventitia: Longitudinal smooth muscle bundles; continuous milking of blood towards heart

Question 9

Atherosclerosis histopathology?

Answer 9

Lesions of T. intima called atheroma or fibro fatty plaques that protrude into and obstructs the vascular lumen

• excessive LDL oxidized by free radicals produced by endothelial cells
• Smooth muscles become fatty and macrophages engulf oxidized LDL forming foam cells; proliferate and secrete collagen and other ECM which thickens T. intima forming fatty streaks

Question 10

Continuous capillary location

Answer 10

fat, muscle, nervous system

Question 11

Fenestrated capillary location

Answer 11

intestinal villi, endocrine glands, kidney glomeruli

Question 12

Discontinuous (aka discontinous) capillary location

Answer 12

liver, bone marrow. spleen