Histology Flashcards
Three layers of the heart wall, from outer to inner
Epicardium
Myocardium
Endocardium
The ___ is called the visceral layer of the serous pericardium. It includes what components?
Epicardium
- mesothelial lining covers external surface
- loose CT and adipose tissue under medothelium (nerves and blood vessels pass through here)
The ___ is the principal component of the heart wall. It is formed by ___, and the ___ is thicker than the ___
Myocardium
Cardiac muscle
Myocardium of the ventricles is thicker than that of the atria
Components of the endocardium:
- Endothelium
- Subendothelial CT
- Impulse-conducting system of the heart (deeper layer of CT)
Heart walls are supported by ___
Fibrous skeleton that also extends into valves
The internal fibrous skeleton consists of ___
4 fibrous rings that surround the valve orifices
2 trigones which connect the rings together
-These are composed of DICT
Rings and trigones of the internal fibrous skeleton of the heart
- Rings: pulmonary trunk, aorta, left atrioventricular ring (mitral valve), right atrioventricular ring (tricuspid valve)
- Left and right fibrous trigone
What do the left and right trigones of the internal fibrous skeleton connect?
- left connects left atrioventricular and aortic fibrous rings
- right connects left and right atrioventricular fibrous rings
The membranous part of the interventricular septum does not have ___. It is composed of ___ and contains part of the ___
Cardiac muscle
DICT
atrioventricular bundle
Valves are composed of ____
CT covered with endothelium
- loose Ct acts as a shock absorber.
- DICT with elastic fibers provides structural support
Valves are composed of ___ layers:
- Fibrosa (ventricular side)
- Spongiosa (core)
- Atrialis (atrial side)
Layers of valves:
Fibrosa
DICT connected to corresponding fibrous ring
Extends from the base along the ventricular side of the atrioventricular valves
Layers of valves:
Spongiosa
Loose CT with a lot of elastic fibers
Most prominent in the free edge of the valve
Shock absorber
Dampens vibrations when the valve closes
Can sometimes have a few adipose tissue cells
Layers of valves:
Atrialis
Proteiglycans and elastic fibers, occasionally smooth muscle cells
Covers the atrial aspect of the spongiosa
What causes mitral valve prolapse?
Abnormal formation of structural proteins (such as collagen or fibrillin)
*fibrillin mutations cause Marfan syndrome, these patients tend to suffer from mitral valve prolapse
The primary pacemaker of the heart is the ___ and the secondary is the ___
SA node (sinoatrial) AV node (atrioventricular)
Cardiac muscle contracts independently of ___. The autonomic nervous system ___
Nerve stimulation
Regulates the heartbeat, but does NOT initiate it
Parasympathetic nerves ___ the heart rate.
Sympathetic nerves ___ the heart rate.
*epinephrine, thyroid hormones, caffeine?
Decrease
Increase
*increase heart rate and force of contraction
Cardiac conducting cells are called ___, and they form what?
Purkinje fibers
-SA and AV nodes and the bundle of His
Myocardial infarctions are caused by
obstruction of coronary arteries and loss of blood supply to the cardiac muscle for more than 20 minutes
Myocarditis is __, and is caused by __.
- The inflammation of the myocardium
- Infection or intoxication
One of the more common tumors of the heart is a ___.
It is (being/malignant).
It is most commonly found __
It is best identified using __
Myxoma
Benign
Left atrium
Echocardiography
Malignant tumors of the heart usually originate __
One of the most common is ___
Rare?
- Elsewhere and then metastasize to the heart
- melanoma
- a rare tumor that actually starts in the heart is angiosarcoma (1/3 of all malignant tumors that originate in the heart)
Cardiomyopathy results in __
Changes in the struct re of the cardiac muscle
Weakens the heart
The walls of arteries and veins are composed of ___ layers, called ___. Name them
3 Tunics Tunica intima Tunica media Tunica adventitia
How do you differentiate between different arteries and veins?
Composition and thickness of the 3 tunics
Components of the tunica intima of vessels
Endothelium Subendothelial CT (loose CT) Internal elastic lamina
Endothelial cells of the tunica intima:
Functions:
Selectively permeable barrier
allows movement from blood to underlying tissue
- simple diffusion for small uncharged molecules (oxygen or CO2)
- others have different pathways
Endothelial cells of the tunica intima:
Selectively permeable barrier:
Pathways
- Transcellular for active transport
- Paracellular pathway for passive transport across zonula occludens
- Gaps or fenestratuons
Endothelial cells of the tunica intima:
Selectively permeable barrier:
Pathways:
Transcellular pathway
uses pinocytic vesicles (or calveolae)
- calveolae use clathrin-independent form of endocytosis (for glucose)
- clathrin-dependent endocytosis is used for LDL and cholesterol
Endothelial cells of the tunica intima:
Function:
Non-thrombogenic barrier
Between platelets and subendothelial tissue
- produce anticoagulants such as thrombomodulin
- damage to endothelial cells causes them to release prothrombogenic agents, such as von Willebrand factor, which leads to clotting
Endothelial cells of the tunica intima:
Function:
Blood flow control
- Vasoconstriction-endothelin, thromboxane, and ACE (angiotensin-converting enzyme)
- Vasodilation-NO and prostacyclin
Endothelial cells of the tunica intima:
Function
Immune response
Through regulation of lymphocyte adhesion and production of several interleukins (IL-1, 6, 8)
Endothelial cells of the tunica intima:
Function
Metabolic and hormonal activity
- Production of growth factors
- CSF (colony-stimulating)
- PDGF (platelet-derived)
- TGF beta (transforming)
- fibroblast GF
Endothelial cells of the tunica intima:
Function
Converting __ to ___ in the presence of ___
Angiotensin I to II in the presence of ACE
The internal elastic lamina of the endothelial cells of the tunica intimate separates ___ from ___ and is composed of ___
- tunica intimate from media
- flattened fenestrated sheet of elastin
The tunica media of blood vessels is composed of ___. It is more well-developed in ___, and includes ___ and ___
- Smooth muscles
- Arteries
- Circular smooth muscle fibers and an external elastic lamina the separates tunica media from tunica adventitia
The tunica adventitia of blood vessels is composed of ___ and includes the following 4 elements:
CT
- Longitudinal smooth muscle fibers
- Loose CT primarily on the periphery
- Vasa vasorum
- Nervi vasorum
Vasa vasorum are __
Small blood vessels that supply the walls of the larger blood vessels
Nervi vasorum are ___
Nerves that innervate blood vessels and travel through the tunica adventitia
3 major types of arteries
- Large elastic, which are conducting vessels
- Muscular, which are medium-sized distributing vessels
- Small arteries and arterioles, which are resistance vessels
The pulmonary artery and the aorta are what kinds of arteries? What others are of the same type?
Large elastic
Subclavian
Common carotid
Large elastic arteries:
Tunica intima
Layers
- Endothelium
- Subendothelial layer (contains collagen and elastic fibers)
- InternL elastic lamina (inconspicuous)
Large elastic arteries:
Tunica intima
Endothelium
Endothelial cells contain rod-like inclusions called Weibel-Palade bodies, which contain bin Willebrand factor, which plays an important role in coagulation.
Antibodies to con Willebrand factor can be used to ___
Identify endothelium-derived tumors (e.g. Angiosarcomas)
Large elastic arteries:
Tunica media
Contains?
Extremely thick
- elastic lamellae (formed by elastin) form concentric layers between muscle cells
- circularly arranged smooth muscle fibers
In individuals with ___, the thickness of the tunica media and the number of the elastic lamellae in large elastic arteries increases
Hypertension
Large elastic arteries:
Tunica adventitia
Contains?
Relatively thin
- collagen and elastic fibers, fibroblasts, macrophages
- vasa vasorum, nervi vasorum
Main differences between muscular and large elastic arteries
(General)
Muscular are somewhat smaller and have very little elastic material in the tunica media. They also have a more prominent internal elastic lamina.
Muscular arteries:
Tunica intima
Contains?
Thinner than in large arteries, but the same layers:
- Endothelium
- Thin subendothelial layer with collagen and elastic fibers
- Prominent internal elastic lamina
Muscular arteries:
Tunica media
Contains?
- Very few elastic lamellae
- circularly arranged smooth muscle fibers
- well developed external elastic lamina
- thicker than the tunica adventitia
Muscular arteries:
Tunica adventitia
Contains?
- well developed
- collagen and elastic fibers, fibroblasts, macrophages
- vasa vasorum and nervi vasorum are not as abundant as in the large elastic arteries
Small arteries and arterioles contain fewer layers of smooth muscle in the ___.
___ is thin.
Tunica media
Tunica adventitia
Small arteries have up to ___ layers of smooth muscle fibers in the ___. Typically there is ___
8
tunica media
Internal elastic lamina
Arterioles have ___ layers of smooth muscle fibers in the ___.
The ___ is not well developed.
Arterioles control ___ by ___.
They direct blood to where it is most needed
One or two
Tunica media
Internal elastic lamina
Blood flow to capillary network by contracting smooth muscle cells
Atherosclerosis results from __
Components?
The formation of lesions in the tunica intima Components of the lesions: -fibrous tissue -smooth muscle cells -macrophages -foam cells -cholesterol crystals -cell debris
Progression of atherosclerosis lesions causes ___, which eventually may result in ___. Possible consequences are responsible for over 50% of deaths in the US and include MI and strokes
- Disruption of the endothelium, blood stasis, and thrombosis
- occlusion of the vessel
___ are the smallest blood vessels in the body. They do not exhibit ___ and their walls are very ____
- Capillaries
- The three tunics in their walls
- Thin to allow fluids, containing gases, metabolites, and waste products
Each capillary consists of ___. The diameter of a capillary is just large enough for blood cells to pass through one at a time.
A single layer of endothelial cells and their basal lamina.
3 types of capillaries:
- Continuous
- Fenestrated
- Discontinuous
Continuous capillaries are found ___. They are characterized by the presence of ___ between cells. The ___ in these capillaries is continuous.
- in muscle tissue, lungs, and CNS
- occluding junctions
- basal lamina
Fenestrated capillaries are found ___. They are characterized by the presence of fenestrations in the ___, not in the ___ that help filter fluid in.
- in tissues where there is a lot of fluid transport, such as intestinal villi, choroid plexus, renal glomeruli, and endocrine organs
- endothelial cells, not in the basal lamina
Discontinuous capillaries (or ___) are large capillaries found ____. In these rather large capillaries, endothelial cells can be completely separated by ___
- Sinusoids
- Specialized organs such as liver, spleen, and bone marrow
- larger gaps that extend into the basal lamina, which is also fenestrated. This allows the endothelium to act as a filter
Veins generally have ___ walls than arteries. What are the major types of veins?
Thinner 1. Small veins/venules A. Postcapillary venules B. Muscular venules 2. Medium veins 3. Large veins
___ receive blood from the capillaries. They do not have ___. This is the principle site of ____, which is initiated by ___. This is accompanied by ___
- postcapillary venules
- tunica media
- emigration of WBCs into tissue
- histamine and serotonin, which cause an increase in permeability of venules
- edema
The postcapillary venules of the lymphatic organs have ____ and thus are called ___
Tall endothelium
High endothelial venules
Muscular venules collect blood from ___. They have very little ___ and can be up to __ in diameter
Postcapillary venules
Smooth muscle in the tunica media
1 mm
Medium veins are ___ in diameter. The 3 tunics are readily observable. They collect blood from ___
Less than 1 cm
Muscular venules
Medium veins:
Tunica intima
Same layers as arteries:
- Endothelium w/basal lamina
- Very thin subendothelial layer with collagen and elastic fibers
- Very thin internal elastic lamina
Medium veins:
Tunica media
Much thinner than in arteries of the same diameter
Thinner than tunica adventitia (which is different than arteries of the same size)
Medium veins:
Tunica adventitia
Thicker than tunica media Contains: -elastic and collagen fibers -fibroblasts and macrophages -vasa and nervi vasorum
Large veins are ___ in diameter. They deliver blood to ___. The three tunica are readily observable and are similar to the medium veins but ___
More than 1 cm
The heart
The boundaries are not as distinct
Large veins:
Tunica intima
Same layers as in medium veins, but the subendothelial layer of CT is thicker and the internal elastic membrane is prominent (it is very thin in medium veins)
Large veins:
Tunica media
Very inconspicuous
Large veins:
Tunica adventitia
Extremely well developed
Many longitudinally oriented smooth muscle fibers
Valves guarantee ____ and consist of a thin layer of ___
Unidirectional flow
CT covered with endothelial lining
Lymphatic capillaries have ___ permeability than blood capillaries, which allows them to collect ___, which is delivered to ____.
Lymphatic capillaries are most common in ___
greater
Protein-rich fluid from intercellular spaces
Lymphatic vessels (at this point it is called lymph)
Loose CT
Endothelium of the arteries and veins is what type?
Simple squamous
