Histology of Heart and Blood Vessels

Histology of Heart and Blood Vessels

1. Vessels

   • Tunica adventitia
     • connective tissue
     • In contact with ECF
     • Gives support
       • important to maintain shape
   • Tunica media
     • smooth muscle
     • allows tone
       • gives elasticity and contractility
     • regulates blood pressure
     • thicker in arteries
       • thickest in aorta and pulmonary arteries - lots of elastic lamellae to stretch and recoil in response to pulse
     • elastic lamellae
       • look dark under a microscope
     • Dissecting aneurism of aorta
       • blood enters t. media due to wall rupture
   • Tunica intima
     • endothelium
     • collagen
     • in contact with blood
     • selectively permeable
     • makes mediators of inflammation and tone
     • Regulates adhesion of platelets

2. Muscular artieries

   • e.g. carotid, iliac,brachial
   • distribute blood
   • not elastic
   • contractile
     • regulate flow
     • regulate pressure
   • Lots of collagen in adventita
   • layer of elastic lamina between media/intima and media/adventitia

3. Arterioles

   • microscopic
   • regulate flow
   • regulate pressure

4. Capillaries

   • mainly endothelial cells
   • exchange
   • Continuous
     • NO gaps in walls
   • Fenestrated
     • pores
   • Sinusoids
     • in liver and spleen
     • WIDE fenestrations

5. Veins/venules

   • thin/flexible walls
   • more prominent adventitia
   • thin/no t.media
   • valves
   • longitudinal smooth muscle between valves
     • assists flow against gravity

6. Heart

   • pumps blood
   • regulates BP
     • secretes ANP
       • atrial natriuretic peptide
       • stimulated by over stretched atria
       • Increases water and sodium uptake to urine
         • = lowers blood volume
   • valves
     • elastic fibres
     • collagen
   • Epicardium
     • (visceral pericardium)
     • fatty, loose connective tissue
       • nerves
       • vessels
       • coronary arteries
       • mesothelium
         • simple cuboidal
         • adipose tissue
   • Myocardium
     • part which contracts
   • Endocardium
     • endothelium
     • loose connective tissue
     • lots of Purkinje fibres