Heart Histology Flashcards
What is a pericardium?
A double-walled sac containing the heart and the roots of great vessels
What are the 2 types of pericardium?
Fibrous pericardium
Serous pericardium
What is the fibrous pericardium?
The tough, external fibrous layer
- made from thick connective tissue
- attached to the diaphragm
What is the function of the fibrous pericardium?
To hold the heart in place in the chest cavity and protects from infections
What 2 layers does the serous pericardium consist of?
Parietal pericardium
Visceral pericardium
What is the parietal pericardium?
The serous membrane on the inside of the fibrous pericardium
What is the visceral pericardium?
The serous membrane on the surface of the heart
What is the function of the serous pericardium?
Helps to lubricate the heart which prevents friction
What are the 3 layers to the heart?
Endocardium (inner)-thin layer
Myocardium (middle)-thick layer
Epicardium (outer)
What does the endocardium consist of?
3 distinct layers:
- Inner endothelial layer- containing flat endothelial cells
- Middle subendothelial layer- containing regularly shaped collagen and elastic fibres
- Outer subendocardial layer (in some areas)- irregularly shaped collagen, and may contain elements of the cardiac conducting e.g purkinje fibres
What are myofibroblasts?
Myofibroblasts are a differentiated cell type essential for wound healing, participating in tissue remodelling following insult
What does the myocardium consist of?
Composed of cardiac muscle:
- myofibrils and sarcomeres
- central nucleus
- intercalated discs
Variable thickness ( thicker in ventricles as they need to contract)
What is another name for the epicardium?
The visceral pericardium
What does the epicardium consist of?
Flattened mesothelial cells
Vessels supplying the heart
Adipose tissue
What is the significance of the heart having a fibrocartilagenous structure?
- Provides a solid structure for the muscle to contract against
- Means the atrial and ventricular sides of the heart are electrically isolated by the fibrous skeleton
What are the features of cardiac muscle?
- Striated like skeletal muscle
- Single centrally placed nucleus
- Connected by intercalated discs to ensure electrical continuity
What is the contractile mechanism of cardiac muscle?
Ca2+ binds to troponin and exposes myosin-binding site on actin
What is the name of the contractile unit within cardiac (and skeletal) muscle?
Sarcomere
What is the structure of a sarcomere?
Composed of 2 main protein filaments, actin and myosin. These are the structures responsible for muscular contraction.
What is the sliding filament theory?
The sliding filament theory explains the mechanism of muscle contraction.
The theory explains how myosin binds to actin, and the myosin then alters its configuration, resulting in a ‘stroke’ that pulls the actin filament causing it to slide across the myosin filament
How is filament sliding a Ca2+ dependant process?
As the binding of Ca2+ facilitates the myosin and actin-binding
What 3 structures bind together adjacent cardiac myocytes?
Desmosomes
Adherens junctions
Gap junctions
What is the function of the structures binding adjacent cardiac myocytes together?
The arrangement of structures increase the transmission of electrical impulses as there is a direct connection between the cells
As well as increasing structural strength and integrity
What is a desmosome?
A desmosome is a cell structure specialised for cell to cell adhesion
- a type of anchoring junction
- Intermediate filaments of each cell connect to a plaque containing transmembrane proteins. These transmembrane proteins attach 2 adjacent cell surfaces
