Cardiovascular System

Question 1

What primordial layer does the cardiovascular system arise from?

Answer 1

• mesoderm > mesenchyme > angioblastic tissue > cardiovascular system

Question 2

T/F: the cardiovascular system is the first functional system to develop in the embryo

Answer 2

• true, necessary for sufficient nutrients

Question 3

How many heart chambers do fish have? amphibians? turtles? birds? mammals?

Answer 3

Question 4

Describe embryonic development of the cardiovascular system

Answer 4

• cardiogenic field anterior and lateral to neural plate
• anteroposterior folding of the embryonic disk
• caudal fusion of endothelial cells into endocardial heart tubes
• endocardial heart tubes and venous system meet and fuse
• fusion of caudal portion of endocardial heart tubes, surrounded by myoblasts to form the myocardium
• creation of cardiac tube (bulbus cordis, ventricle, atrium)
• loop formation and partitioning of chambers

Question 5

What kind of cells are in the cardiogenic field?

Answer 5

• endothelial cells only

Question 6

What are the main parts of the embryonic heart?

Answer 6

• truncus arteriosus: divided into outflow trunks (aorta and pulmonary)
• atrium: will be divided into L and R atria
• bulbus cordis and ventricle: will be divided into L and R ventricle

Question 7

Describe the development of internal heart structures

Answer 7

• primary atrial septum is forming, ostium primum between primary septum and endocardial cushion allows blood flow from R to L atrium.
• primary atrial septum grows and fuses with the endocardial cushion, closing ostium primum. ostium secundum opens in the primary septum. ventricular septum is growing
• secondary atrial septum grows to the right of the septum primum, forming the foramen ovale. blood still flows from R to L atrium, but secondary septum acts as a valve to prevent backflow. ventricular septum is now complete
• embryo is born, first birth causes pressure drop in heart which causes septum primum to be pushed against the septum secundum resulting in the functional closure of the foramen ovale (morphological closure happens later when fuses: fossa ovalis)

Question 8

When the heart is developing its internal structures, it is also twisting. Why? If it doesn’t what is the result?

Answer 8

• the truncus arteriosus is divided into an ascending aorta and pulmonary trunk by a spiral aortic pulmonary septum, which ensures that blood flows from R ventricle to pulmonary trunk, and L ventricle to ascending aorta
• if this doesn’t occur: straight septum aka TRANSPOSITION OF THE GREAT VESSELS…. which is not compatible with life

Question 9

What are three unique features of fetal circulation that must close soon after birth?

Answer 9

• ductus arteriosus
• umbilical arteries
• foramen ovale

Question 10

What are the functions of the cardiovascular system?

Answer 10

• maintenance of adequate blood flow (cardiac output)
• delivery of O2, nutrients, hormones, electrolytes, and water to peripheral tissues
• removal of O2 and other metabolic waste products
• maintenance of thermoreguation
• maintenance of glomerular filtration rate and urine output

Question 11

What is the path of circulation?

Answer 11

• artery > arterioles > metarteriole > capillaries
  > venule > vein

Question 12

What are features of the heart?

Answer 12

• first organ to form in embryo
• 3 tunics
  
  • endocardium (includes valves)
  • myocardium (heart muscle)
  • epicardium (visceral pericardium)

Question 13

Label the arrows

Answer 13

Question 14

What are some features of endocardium?

Answer 14

• forms inner lining and valves
• equivalent to tunica intima in BV
• endothelial cells on innermost surface
• direct contact w/ blood
• important in hemostasis
• 3 layers

Question 15

Describe the 3 layers of endocardium

Answer 15

• endothelium
• basal lamina
• sub-endothelial connective tissue

Question 16

What is this structure?

Answer 16

• valve cusp

Question 17

What is shown here? What are some features?

Answer 17

• myocardium
• involuntary
• cross-striated
• central single nucleus
• intercalated discs (w/ gap junctions and anchoring junctions)
• lipofuscin
• sarcoplasmic reticulum
• many mitochondria (up to 20% cell volume, requires lots of O2, low generation capacity)

Question 18

What happens if cardiomyocytes are O2 deprived

Answer 18

• hypoxic conditions cause cell death > replaces with fibrous tissue > loss of function

Question 19

What are purkinje cells?

Answer 19

• modified cardiomyocytes that function in conduction
• located in endocardium

Question 20

What are some features of the epicardium?

Answer 20

• outer surface of heart (visceral pericardium)
• surface is covered by mesothelium (simple squamous epithelium), a thin layer of dense CT, and a variably thick layer adipose tissue with blood vessels
• contiguous with the endocardium at the level of the endocardial cushion
• mesothelium cell layer lines opposing parietal surface of the pericardial sac, secreting small amounts of serous fluid that lubricates movement of the epicardium

Question 21

What are some features of the cardiac skeleton?

Answer 21

• 4 dense bands of fibrous connective tissue encircling the base of the pulmonary trunk, aorta, and AV valves
• provides structural support
• a triangular mass of fibrous CT (fibrous trigon) connects the aortic a. ring and L/R atrioventricular rings.
• “Os Cordis” - osseous differentiation of the fibrous trigon, primarily seen in cattle

Question 22

What are the different kinds of vessels?

Answer 22

• arteries (elastic, muscular, arterioles)
• capillaries (continuous, fenestrated, discontinuous/sinusoids)
• veins (venules)
• lymphatic vessels

Question 23

What are the tunics of the vessels? What are some differences between arteries and veins?

Answer 23

• tunica intima (touches blood)
  
  • endothelium, internal elastic membrane, subendotheial CT
• tunica media
  
  • smooth muscle, elastic lamellae/fibers
• tunica adventitia/externa
  
  • collagen, may have blood vessels/nerves/capillaries
• arteries have thick musculature
• veins are thinner and have valves

Question 24

What are the functions of vascular endothelium?

Answer 24

• role in hemostasis
• modulates perfusion
• role in inflammation

Question 25

What are the two kinds of arteries and some features?

Answer 25

- elastic artery - 3 tunics: - tunica intima - tunica media (repeating elastic lamellae) - tunica adventitia (contains vasa vasorum) - muscular artery - tunica media is primarily SMOOTH muscle (thickest layer) - round appearance

Question 26

What is this structure?

Answer 26

- elastic artery

Question 27

What is this structure?

Answer 27

- muscular artery

Question 28

What is this structure?

Answer 28

- elastic artery

Question 29

What are some features of tunica media?

Answer 29

- vascular smooth muscle - regulates diameter and tone - vasodilation/vasoconstriction

Question 30

What are some features of arterioles?

Answer 30

- 1-3 layers of SM cells - greatest effect on blood pressure - nuclei bulge into lumen - round appearance of vessel -no internal elastic membrane in the smallest arterioles with only one SM cell - metarteriole is a terminal vessel, as pre-capillary sphincters that can regulate flow to capillary bed

Question 31

What are some features of capillaries?

Answer 31

- thin-walled tubules of mesenchymal origin - in cross-section they are only one endothelial cell roles into a tube (simple squamous) - represent site of exchange between blood and surrounding tissues - capillary wall is impermeable to proteins, but permeable to many things(O2, CO2, ions,H2O, glucose, aas, fatty acids, vitamins, hormones) - 3 kinds: continuous, fenestrated, discontinuous (sinusoidal)

Question 32

What are the three kinds of capillaries?

Answer 32

Question 33

What is this? What are some features?

Answer 33

- continuous capillary - nucleus of endothelial cell - pinocytotic vesicles - tight junctions - basement lamina/membrane

Question 34

What is this an example of?

Answer 34

- fenestrated capillaries - the Renal corpuscle (glomerulus) is a tightly coiled network of fenestrated capillaries and is responsible for filtration of plasma

Question 35

What is this? What are some features?

Answer 35

- discontinued capillaries (sinusoids) - lumen is enlarged and irregular - lining endothelium is discontinued and fenestrated - basal lamina may be absent

Question 36

What are some features of pericytes (Roujet cells)

Answer 36

- mesenchymal-like cells that wrap around the endothelium of capillaries and venules - communicate with endothelial cells physical contact and paracrine signaling - help maintain homeostatic and hemostatic functions in the brain and sustain the blood-brain barrier - proliferate after injury - stem cell source - important in angiogenesis (new vessel formation)

Question 37

What are some features of podocytes?

Answer 37

- lining the bowman’s capsules (nephrons) - help prevent proteins and other large molecules from being filtered - foot processes extend and wrap around the capillaries of the glomerulus to form filtration slits - the pedicels increase the area of cells enabling efficient ultrafiltration

Question 38

What are some features of venules?

Answer 38

- “postcapillary venules” - “leaky” vessels - no smooth muscle - leukocyte diapedesis possible

Question 39

What is pictured? What are some features?

Answer 39

- vein

Question 40

What are some differences of veins compared to arteries?

Answer 40

- large, wide lumen, thin walls in comparison to similarly sized arteries - valves present - thin tunica media - tunica adventitia is thickest layer - large veins may have vasa vasorum - may be collapsed in histological sections

Question 41

What is this? What are some features?

Answer 41

- lymphatic vessel - very thin wall (smooth muscle) - very low pressure - may contain valves - no RBC in lymph, so appears clear - complementary to the cardiovascular system - freely anastomose with each other - lined by endothelial cells - adventitia binds lymph vessels to surrounding tissue