Lecture 3: Cardiac and Vascular Function Flashcards
Look art the gross anatomy
Now
Describe the pericardium
Fibrous pericardium (anchor)
Parietal pericardium
Visceral pericardium / epicardium
Describe the layers of the heart
Epicardium
Myocardium
Endocardium
Describe the differences between the heart chambers
2 Ventricles (left wall thicker) IV septum
2 Atria - Thin walled
- Blood stored here (reservoirs)
Apex, Base
Describe the fibrous skeleton
Separates the Atria and Ventricles and which valves are mounted
- Prevents electrical conduction except via the bundle of his
Describe the aorta
Thick walled elastic artery
What do the aorta and PA do during systole and diastole?
Stretch during systole and release this energy back into the blood during diastole, pushing blood into the peripheral circulation
Describe the AV valves
Large openings (low pressure gradient) Thing leaflets Chordae tendon attached to papillary muscles
Tricuspid and mitral valves
Describe the semilunar valves
Three half moon cusps attached around valve rings (semilunar)
Describe the composition of the myocardium:
Cells : Myocytes and non-myocytes
ECM
Vascular tissue
How much of the myocardium is composed by myocytes?
30% of cells are myocytes and they make up 70% of myocardium by volume
What are the non-myocytes in myocardium?
Fibroblasts (90% of non-myocyte cells)
Endothelial cells
Vascular smooth muscle
Macrophages
Together form 67% of cells in myocardium
Whats in the ECM of myocardium?
Collagen Elastin Cells Vessels Nerves Gel metric molecules Growth Factors Cytokines Enzymes
How much myocardium is composed of vascular tissue?
60% of extracellular space is vascular tissue
Describe the relative sizes of a myocyte
80-100 micrometers in length
20 micrometers in diameter
What are the myofilaments in a myocyte?
Actin and myosin
What is a prominent anchor protein in myocytes?
Titan
Describe the structure of titan
Long fibrous protein that links myosin molecules to the z-disc
Whats the function of titan?
Dominates elasticity at short sarcomere lengths
Keeps myosin entered within the sarcomere
Generates the passive stiffness of myocytes
Describe some landmarks of the myocyte
- Sarcomeres are the contractile units
- Z lines
- SR
- T tubules near z lines
- Mitochondria
- Capillaries
- Myogenic
Describe the end junctions of between myocytes
Syncytium created by intercalated discs composed of:
- Gap Junctions
- Adhering Junctions
Describe the junctions between myocytes
Endomysial cords
How do heart attacks influence nexus unctions?
Heart attacks alters pH and thus nexus junction function
What is the current view that describes the cellular organisation of the ventricular myocardium:
Continuous branching syncytium, changing fibre orientation across the ventricular wall.
What defines muscle fibre orientation?
The average direction of the cell axis in a region is said to define the fibre orientation.
Therefore cardiac muscle fibre is inappropriately used as it suggests macroscopic similarities between cardiac and skeletal muscles.
Whats the current view on myocardium being continuous?
Myocardium is not a continuous structure- it is laminar.
It is said to be a discontinuous continuum.
Describe the relationship between fibre orientation and electrical conduction
The electrical activation travels fastest along the plane of the myocyte.
Describe muscle fibre orientation across the heart wall
Direction of myocyte orientation changes across the wall of the heart b/c different layers have different circumference.
Orientation reduces the length of contraction require
Describe how laminar structure works
- Layers slide over one another (shear)
- Layers influence spread of electrical activation
Describe electrical activation of the heart from the purkinje network
Perkinje- endo - epi and therefore spreads in myocyte plane
What allows electrical conduction between adjacent myocytes?
Collagen between fibrils.
In heart structure what does collagen determine?
Collagen determines architecture and electrical + mechanical function
What collagen has been found in myocardium?
1, 3,4,5,6
What are the main types of collagen in myocardium?
1 and 3 are the main constituents of the ECM. Representing 85% and 11% of the total collagen content respectively.
What is the function of collagen type one in myocardium?
Collagen has a high tensile strength, stiffness. (makes up major collagen cords)
Abundant in epimysium and perimysium.
What is the function of collagen type 3 in myocardium?
type 3 collagen is the principle component of fine collagen fibrils that compose highly deformable reticular networks and in the heart can be found in epi- and perimysium but is more prominent in the endocardium.
What is collagen organisation related to?
Collagen organisation is tightly related to the layered myocyte organisation
How is extracellular connective tissue defined by:
Based on location/ function categorised into:
- Endoymysium
- Perimysium
- Epimysium
What is endomysium?
Connective tissue surrounding individual myocytes or connecting adjacent myocytes to each other and capillaries.
What is perimysium?
Connective tissue surrounding groups of myocytes or connecting adjacent muscle groups.
Crimped collagen cords which run parallel to the myocyte axis are defined as perimysial fibres.
What is epimysium?
Connective tissue surrounding the muscle - inside and outside surfaces of the heart.
What is the connective tissue heirachy essential for?
The connective tissue heirachy interconnecting groups of myocytes is essential for the efficient coupling of forces across and around the ventricular walls during contraction.
It also limits overextension of myocytes so that they work at efficient sarcomere lengths
What is the specialised conduction system needed for?
- Coordinates spread of electrical activation
- Needed for efficient pumping mechanism
Where do coronary arteries originate from?
Coronary arteries originate from the coronary ostea in the aorta.
What is the function of the coronary arteries?
Supply the heart muscle with oxygen and nutrients
What do the coronary veins do?
Drain back in parallel system. (coronary sinus is where it drains back into the RA)
What does impaired coronary circulation lead to?
Heart attacks and angina.
What sort of vascular beds can the coronary system been seen as?
The coronary bed can be seen as one the of parallel systemic circuits
What can heart disease modify?
Myocyte structure, connective tissue structure.
