02: Histology: Heart & Blood Vessels Flashcards
Describe the structure and function of lymphatics.
- Structure:
- Endothelium fenestrated & non-fenestrated
- Basement membrane continuous or non-continuous
- Have valves
- Large lymphatics have muscle in wall
- Function: drain clear fluid (lymph) from tissue space (more permeable than capillaries); chyle is a milky substance of lymph and emulsified fats formed in small intestines and taken up by lacteals (lymph vessels).
Identify this picture.
Lymphatic vessel with valve.
Identify the layers of the human aorta.
- Intima
- Media
- Adventitia
NB: Layers separated by internal/external elastic laminae.
What is endothelium?
Lining of blood vessels and lymphatics.
DO NOT confuse with epithelium (covering body surface or lining organs)
Identify the components of the intima layer of blood vessels.
-
Endothelium:
- Continuous (via tight junctions)
- Fenestrated (in intestines, endocrine organs, glomeruli)
- Basal lamina (layer of extracellular matrix secreted by the endothelial cells)
- Myointimal cells (smooth muscle, produce collagen, phagocytic ability)
NB: no smooth muscle in capillaries
Identify the types of capillaries.
- Continuous (e.g., muscle)
- Fenestrated (fenestrations within endothelial cells; e.g., endocrine glands)
- Sinusoidal (gaps between endothelial cells; e.g., liver)
Identify this structure and its layers.
Identify this structure and the components marked by the arrows and arrowheads.
Continuous capillary in skeletal muscle.
Arrowheads = tight junctions
Arrows = pinocytotic vessels
Identify this structure.
Capillary in endocrine gland (note fenestrations).
Identify this structure.
Capillary of liver (note sinusoids).
Name the 8 functions of the endothelium.
- Barrier - via tight junctions
- Filter & transport - fenestrations, pinocytotic vesicles, active transport via proteins (BBB)
- Secretion - vasodilation (prostacyclin, nitric oxide) & vasoconstriction (angiotensin-converting enzyme [ACE], enothelin)
- Cell growth - increase via PDGF or decrease via heparin, TGF-beta
- Clotting - inhibit (prostacyclin & NO inhibit platelet aggregation, tissue plasminogen activator regulates fibrinolysis, thrombomodulin) or promote (tissue factor, platelet activating factor, von Willebrand factor)
- Lipoprotein metabolism - oxidation of low density lipoproteins (LDL) and VLDL
- Extracellular matrix production - Type IV collagen, laminin, proteoglycans
- Immunologic - activated by cytokines to produce adhesion molecules (selectins, integrins, CD markers); regulate immune functions (IL-1,6,8); express histocompatability antigens (HLA-I,II)
Identify the components of the media layer of blood vessels.
- Elastic fibers: circumferentiall oriented
-
Smooth muscle cells: regulate blood pressure and blood flow
- Make collagen, elastin, proteoglycans
- Migrate to intima and proliferate
- Stimulated by PDGF, endothelin, FGF
- Inhibited by nitric oxide, TGF-beta
Identify the structures in this slide.
- Internal elastica
- External elastica
Describe the innervation of the media in blood vessels.
- Adrenergic: vasoconstriction
- Cholinergic: vasodilation
- Afferent: pressure receptors, chemoreceptors
NB: Carotid bodies connect by the glossopharyngeal nerve to the brainstem.
Identify the components of the adventitia layer of blood vessels.
- Connective tissue
- Vasa vasorum: network of small blood vessels that supply the walls of large blood vessels
What is the function of microvascular arterio-venous shunts?
Located in fingers, toes, ears and nose; act to preserve heat centrally.
What is the function of high endothelial venules?
Facilitate lymphocyte adhesion and migration; have receptors (GlyCAM-1, ICAM-1, CD34) for ligands on naive lymphocytes (CCR7, L-selectin, LFA-1).
Describe the major differences between arteries and veins.
- Arteries: high pressure, thicker media, well-defined elastic layers
- Veins: low pressure, valves, thicker adventitia
What is a hemangioma?
Benign and usually self-involuting tumor (swelling or growth) of the endothelial cells that line blood vessels, and is characterised by increased number of normal or abnormal vessels filled with blood.
List the components of the heart.
- Epicardium
- Myocardium & conduction system
- Valves
- Endocardium
Describe the epicardium of the heart.
The mesothelium (M) lines the visceral and parietal pericardium.
Describe the cells comprising the myocardium of the heart.
- Comprised of myocytes, responsible for contraction.
- The atrial cells also secrete B-type natriuretic protein (BNP) when stretched:
- Increase water, sodium & potassium excretion by kidney
- Inhibit renin secretion by kidney (renin increases BP)
- Inhibit aldosterone secretion by adrenals (aldosterone increases BP)
Identify the structures labelled in the picture:
This is a myocyte.
D = desmosome
FA = fascia adherens
G = glycogen
M = mitochondrion
N = gap junctional nexus
SR = sarcoplasmic reticulum
T = T-tubules
Identify the components of the myocardium.
- Myocytes
- Conduction system composed of specialized muscle cells
- Nerves
- Connective tissue
- Vessels
- Leukocytes (macrophages, mast cells, lymphocytes)
Describe the myocardial conduction system.
- Specialized myocytes which are transducing electrical impulses rather than contracting.
-
Sinoatrial (SA) node: the pacemaker
- At junction of SVC with atrium
- Desmosomes connect instead of intercalated disks
- Embedded in connective tissue with central nodal artery
-
Atrioventricular (AV) node:
- Adjacent to opening of coronary sinus above tricuspid valve ring
- Small fibers in connective tissue
-
Bundle of His
- Left bundle branch: diffuse fan of fibers
- Right bundle branch: more distinct
- Connect with Purkinje fibers (myocytes with abundant glycogen and few myofibrils) in ventricles
Describe the endocardium of the heart.
- Collagen, elastic fibers, smooth muscle cells, endothelium (but mainly connective tissue)
- Thickness determined by pressure and turbulence
Describe the components of the heart valves.
- Spongiosa - looser connective tissue layer
- Fibrosa - denser connective tissue
- Covered by endothelium
- Valve rings connect to the central fibrous body of the heart
- No blood vessels in the normal valve
Identify the below structure and its components-
Name the cardiomyopathies:
A) Hypertrophic
B) Normal
C) Dilated
What cardiomyopathy is shown below?
Myocyte disarray in hypertrophic cardiomyopathy.
What are the most common sites of mutations in familial hypertrophic cardiomyopathy?
- Beta-myosin heavy chain (35%)
- Troponin T (15%)
- Myosin-binding protein C (15%)
- Alpha-tropomyosin (5%)
- Myosin light chain (1%)
