CARDIOVASCULAR SYSTEM & LYMPHATICS & BLOOD

• CIRCULATORY SYSTEM

  • pumps and directs blood cells and substances carried in blood to all tissues of the body
• Endocardium

  • consists of a very thin inner layer of endothelium and supporting connective tissue, a middle myoelastic layer of smooth muscle fibers and connective tissue
• Myocardium

  • Consists mainly of cardiac muscle with its fibers arranged spirally around each heart chamber 
  • thicker in the walls of the ventricles, particularly the left, than in the atrial walls
• Epicardium

  • a simple squamous mesothelium supported by a layer of loose connective tissue containing blood vessels and nerves
  • corresponds to the visceral layer of the pericardium
• Heart

  
• Epicardium or visceral pericardium

  A) Mesothelium

  B) connective tissue

  C) nerves

  D) epicardium

  E) fat

  F) myocardium

  
• Cardiac skeleton

  • Dense irregular fibrous connective tissue
  • forms part of the interventricular and interatrial septa, surrounds all valves of the heart, and extends into the valve cusps and the chordae tendineae to which they are attached
• Fibrous cardiac skeleton of heart

  A) chordae tendineae

  B) atrium

  C) ventricle

  D) endocardium

  E) myocardium

  F) connective tissue

  
• Conducting system of the heart 

  • generates and propagates waves of depolarization that spread through the myocardium to stimulate rhythmic contractions 
  • sinoatrial (SA) node (or pacemaker) and the atrioventricular (AV) node → AV bundle (of His) → subendocardial conducting network.

  
• Heart valves

  • composed of connective tissue with overlying endocardium.
  • 3 layers

  • Fibrosa - core of the valve and contains fibrous extensions from the dense irregular connective tissue of the skeletal rings of the heart.

  • Spongiosa - loose connective tissue located on the atrial or blood vessel side of each valve

  - shock absorber

  • Ventricularis - adjacent to the ventricular or atrial surface of each valve and is covered with endothelium.

  A) spongiosa

  B) fibrosa

  C) ventricularis

  
• TISSUES OF THE VASCULAR WALL

  • Endothelium

  -specialized epithelium that acts as a semipermeable barrier between two internal compartments: the blood plasma and the interstitial tissue fluid.

  -Vascular endothelial cells are squamous, polygonal, and elongated with the long axis in the direction of blood flow.

  - nonthrombogenic surface

  • Smooth muscle
  • Connective tissue

  
• Tunica intima

  • the innermost layer of the vessel
  • Endothelium - a single layer of squamous epithelial cells
  •  basal lamina of the endothelial cells (a thin extracellular layer composed chiefly of collagen, proteoglycans, and glycoproteins)
  • subendothelial layer - loose connective tissue.
• Tunica media

  • consists primarily of circumferentially arranged layers of smooth muscle cells.
  • In arteries, the media may have a thin external elastic lamina, separating it from the outermost tunic
• Tunica adventitia

  • composed primarily of longitudinally arranged collagenous tissue (type l) and a few elastic fibers 
  • Contains the vasa vasorum and nervi vascularis
• LAYERS OF VASCULAR WALL

  A) tunica intima

  B) endothelium

  C) subendothelial layer

  D) internal elastic lamina

  E) tunica media

  F) external elastic lamina

  G) tunica externa

  H) vasa vasorum

  
• Elastic arteries

  • the aorta, the pulmonary artery, and their largest branches
  • called conducting arteries because their major role is to carry blood to smaller arteries 
  • most prominent feature - the thick media 
  • in which elastic lamellae alternate with layers of smooth muscle fibers

  
• Muscular Arteries

  • distribute blood to the organs and help regulate blood pressure by contracting or relaxing the smooth muscle in the media
  • intima has a very thin subendothelial layer and a prominent internal elastic lamina

  
•  Arterioles

  • smallest arteries branch
  • only one or two smooth muscle layers 
  •  indicate the beginning of an organ's microvasculature 
  • flow regulators for the capillary beds
  • slight thickening of the smooth muscle at the origin of a capillary bed from an arteriole is called the precapillary sphincter.

  
• Capillaries

  •  form blood vascular networks that allow fluids containing gases, metabolites, and waste products to move through their thin walls
  • Each consists of a single layer of endothelial cells and their basal lamina
  • always function in groups called capillary beds
• Continuous capillaries

  • distinct continuity of the endothelial cells in its wall.
  • most common type of capillary 
  • found in all kinds of muscle tissue, connective tissue, exocrine glands, and nervous tissue

  
• Fenestrated capillaries

  • characterized by the presence of small circular fenestrae through the very thin squamous endothelial cells 
  • Each fenestra is usually covered by a very thin diaphragm
  • the kidney, the intestine, the choroid plexus and the endocrine glands

  
• Sinusoidal capillaries

  • endothelial cells have large fenestrae without diaphragms; the cells form a discontinuous layer and are separate from one another by wide spaces; the basal lamina is also discontinuous.
  • irregularly shaped
  • liver, spleen, some endocrine organs, and bone marrow

  
• Sinusoidal capillary

  A) adipocytes

  B) hematopoietic cells

  C) sinusoid

  
• name it

  A) precapillary sphincters

  B) metarteriole

  C) arteriole

  D) lymphatic capillary

  E) anchoring filaments

  F) venule

  G) thoroughfare channel

  
• Post capillary Venules

  • collect blood from the capillary network
  • characterized by the presence of pericytes.
  • PERICYTES

  -cells of mesenchymal origin with long cytoplasmic processes partly surrounding the endothelial layer

  -provide vascular support and promote stability of capillaries and postcapillary venules

  
• Medium Veins

  • diameter of as much as 10 mm.
  • Valves are a characteristic feature of these vessels
  • most numerous in the inferior portion of the body, particularly the lower limb

  
• Large Veins

  • diameter greater than 10 mm
  • tunica adventitia of large veins (subclavian veins, portal vein, and the venae cavae) is the thickest layer of the vessel wall
  • tunica adventitia also contains longitudinally disposed smooth muscle cells

  
• Arteriovenous shunts

  • Direct routes between the arteries and veins that divert blood from the capillaries
  • found in the skin of the fingertips, nose, and lips and in the erectile tissue of the penis and clitoris.
  • often coiled, has a relatively thick smooth muscle layer, is enclosed in a connective tissue capsule, and is richly innervated.

  
• Coronary arteries

  • considered to be medium-sized muscular arteries
  • originate from the proximal part of the ascending aorta and lie on the surface of the heart in the epicardium surrounded by adipose tissue.

  
•  Dural venous sinuses

  • venous channels in the cranial cavity.
  • broad spaces within the dura mater that are lined with endothelial cells and devoid of smooth muscles
• Great saphenous vein

  • a long subcutaneous vein of the lower limb that originates in the foot drains into the femoral vein just below the inguinal ligament
  • possesses numerous longitudinal smooth muscle bundles in the intima and in the well developed adventitia

  
• Central adrenomedullary vein

  • Passes through the adrenal medulla and its tributaries have an unusual tunica media 
  • contains several longitudinally oriented bundles of smooth muscle cells that vary in size and appearance (MUSCLE CUSHIONS)

  
• Lymph

  • excess interstitial fluid
• Lymphatic capillaries (or lymphatics)

  • originate as closed-ended vessels consisting of a single layer of very thin endothelial cells on an incomplete basal lamina.
• Lymphatic vessels

  • resembles that of veins except with thinner walls and no distinct separation among tunics

  
• Lymphatic vessels and valve