Lecture 7 - Histo Of The Heart Flashcards
What are the features of smooth muscle
- fibers are fusiform
- no visible striations
- low, continuous force
How do SM contract
They condense toward focal densities which cause them to shrivel
How are cardiac muscles organized
Short, branched and Y shaped with extensive capillaries
What are intercalated discs
Transverse junctions at the ends of cells that allow passage of electrical current
What are purkinje cells
Modified cardiac muscle cells that act as pacemaker cellsq
What is the fibrous pericardium
Outer covering of dense connective tissue (dense irregular)
What are the parts of the serous pericardium
Parietal layer, visceral layer, and pericardial cavity
What is the parietal layer of serous pericardium
Lines the inner surface of the fibrous pericardium
What is the visceral layer of serous pericardium
Covers the outer surface of the heart
What is the space between the parietal and visceral pericardium
Pericardial cavity
What are the layers of the heart
Epicardium, myocardium, endocardium
What is in the epicardium layer
Visceral layer of serous pericardium
What is in the myocardium
Cardiac muscle
What is in the endocardium
Areolar or loose CT AND endothelium
What cell type is found in endocardium
Simple squamous; flat cells that reduce drag in the area
What portion of the heart covers the valves
Endocardium
What kind of CT is found in epicardium
Mostly loose CT but has pockets of dense
What layer do we find coronary arteries? What are they embedded in?
Epicardium, adipose
Which layer of the heart has mesothelium
Epicardium
What layer is synonymous with visceral pericardium
Epicardium
What is the thickest layer of the heart
Myocardium
What are contained in the myocardium
Cardiomyocytes, nodal cardiomyocytes, myoendocrine cardiomyocytes
What do myoendocrine cardiomyocytes contain
Atrial granules; contain precursor of ANF (atrial natriuretic factor)
What does ANF do?
Targets kidneys to decrease Na and H2O retention
What kind of t-tubules do myocardium have
Diad
What is the orientation of the intercalated disc
Always perpendicular to fibers
What is the adhesion site of the intercalated discs
Fascia adherens
What are actin filaments at the end of terminal sarcomeres that insert into the interdigitating junction
Fascia adherens
What are the 2 types of regions and their subcategories in the interdigitating junction
Transverse
- fascia adherens
- desmosomes
Longitudinal
-gap junction
What are desmosomes?
They are transverse regions that provide anchorage for the intermediate filaments in the cytoskeleton
What are gap junctions
Longitudinal junctions that allow excitation to pass between cells since they are low resistance
What is the difference between t-tubules in cardiac muscle and skeletal muscle
Card
- they are diads
- 1 t-tubule and 1 SR cisterna
Skeletal
- triad
- 1 t-tubule and 2 SR cisternae
What is the purpose of T-tubules
They distribute Ca to all muscle fibers in a bundle which permits uniform contraction
What causes liver spots on the skin
Lipofuscin granules
What are lipofuscin granules
Small bodies that accumulate with age in stable and non-dividing cells
They contain matter derive from lysosomal digestion
What are the layers of endocardium
Endothelium (simple squamous) and thin layer of loose CT (areolar)
What is subendocardial layer? What is unique
This is a thin layer of CT with smooth muscle that contains purkinje fibers
It is only found in ventricles
Where are the purkinje fibers in the atria
They are often closer to the endothelium and intermixed with myocardium
What is the general path of electrical signals
Sinoatrial (SA) node —> atrioventricular (AV) node —> AV bundle (Bundle of His) —> R/L bundle branches —> purkinje fibers
What are nodal cardiomyocytes
Modified cardiomyocytes within the SA/AV nodes that relay electrical signals
What are subendocardial branches
cells that transmit signal to ventricular cardiomyocytes
What kind of CT is the cardiac skeleton
Dense, irregular CT located in the endocardium
What is the purpose of the cardiac skeleton
- Anchors valves and surrounds AV canals to maintain shape
- Contribute to interventricular and interatrial septa
- Extends into the valve cusps and chordae tendinae
- insertion of cardiac muscle
- electrical insulator between atria and ventricles
What does dense, irregular CT have a lot of
Collagen
What are the heart valves continuous with
Cardiac skeleton
What is the composition of a heart valve
The core is fibroelastic CT (lamina fibrosa) covered by endothelium
The fibroelastic layer condenses to form a valve ring (central portion of valve)
What are the layers of vessels? How are they different in arteries and veins
Tunica intima (innermost) Tunica media Tunica adventitia or externa (outermost)
The media is bigger in arteries and the externa is bigger in veins
What is in the tunica externa
Fibroblasts, elastin, collagen, vaso vasorum, and nerves
The CT functions to keep anchor vessels to an organ
What is the vaso vasorum? Where is it found
Blood vessels that feed the layers of larger vessels
Tunica externa
What is contained in the tunica media
SM, elastic and reticular fibers, and sensory fibers as well as external elastic lamina
What is in the tunica intima
Endothelium Subendothelium (loose CT) Basal lamina (Type 4 collagen) Internal elastic lamina (allows some of the force of contraction to be absorbed
Where are the valves of veins contained
Tunica intima
Where are elastic fibers found in the great arteries
All 3 layers
What are some of the elastic arteries in the body
Aorta Brachiocephalic trunk Common carotid Subclavian Pulmonary arterial vessels
What are the 2nd to largest size of A?
Muscular A
What are the characteristics of the muscular A
They have internal and external elastic lamina
Proportionally thicker tunica media
Most named A are muscular
What do arterioles not have
Internal elastic lamina
How thick is the tunica intima of arterioles
1 layer thick
What arteries are most dynamic in size
Arterioles
Sympathetic affects on arterioles? Parasympathetic?
Symp
-vasoconstriction = raise BP
Parasymp
-vasodilation = lower BP
How thick is the tunica intima in capillaries
1 cell
What is the primary function of capillary beds
Waste drop off and nutrient pick up
What controls the flow of blood through caps
Pericytes
What brings blood into a capillary bed
Metarterioles
What are true capillaries
Branches off of the metarteriole with rings of SM on their walls
What is a thoroughfare channel
Direct channel through capillaries without branching
What do capillary beds drain into
Postcapillary venule
What are some roles of endothelial cells in the capillaries
They support basement membrane
Produce collagen
Metabolically involved in blood coag and thrombosis
Involved in vasodilation and constriction
What are the capillary types from most open to least
Sinusoid (discontinuous) , fenestrated, continuous
What are some examples of continuous capillaries
Thymus barrier, blood brain, blood and testes
What are some examples of fenestrated capillaries
Kidneys, endocrine organs, intestinal walls, choroid plexus
What are some examples of sinusoidal capillaries
Bone marrow, liber, and spleen
Where is 60% of the body’s blood at rest
Venules - they function as blood reservoirs
Do venules have valves
No, but veins do
Where do veins/venules usually travel
With their companion A
Which veins have well developed tunica media
Med/large
What level of veins have vasa vasorum
L
What do the pressure differences across capillaries cause
Flow into lymph vessels
How are lymph and veins similar
they both have one way valves to ensure that flow is unidirectional
how do lymphatic endothelial cells compare to caps
the lymph cells are larger
What does a lymphatic vessel lack
basal lamina
What layers do lymphatic vessels have
tunica intima, media, externa
what should not be in lymph vessels
RBC
What does the thoracic dudct drain into
braciocephalic v
