Histology of Heart and Blood Vessels

1. Tunica adventitia
   1. connective tissue
   2. In contact with ECF
   3. Gives support

      Nota:

      • important to maintain shape
2. Tunica media
   1. smooth muscle
   2. allows tone

      Nota:

      • gives elasticity and contractility
   3. regulates blood pressure
   4. thicker in arteries

      Nota:

      • thickest in aorta and pulmonary arteries - lots of elastic lamellae to stretch and recoil in response to pulse
   5. elastic lamellae

      Nota:

      • look dark under a microscope
   6. Dissecting aneurism of aorta

      Nota:

      • blood enters t. media due to wall rupture
3. Tunica intima
   1. endothelium
   2. collagen
   3. in contact with blood
   4. selectively permeable
   5. makes mediators of inflammation and tone
   6. Regulates adhesion of platelets

Nota:

• e.g. carotid, iliac,brachial

1. distribute blood
2. not elastic
3. contractile
   1. regulate flow
   2. regulate pressure
4. Lots of collagen in adventita
5. layer of elastic lamina between media/intima and media/adventitia

1. microscopic
2. regulate flow
3. regulate pressure

1. mainly endothelial cells
2. exchange
3. Continuous
   1. NO gaps in walls
4. Fenestrated
   1. pores
5. Sinusoids

   Nota:

   • in liver and spleen
   1. WIDE fenestrations

1. thin/flexible walls
2. more prominent adventitia
3. thin/no t.media
4. valves
5. longitudinal smooth muscle between valves

   Nota:

   • assists flow against gravity

1. pumps blood
2. regulates BP
   1. secretes ANP

      Nota:

      • atrial natriuretic peptide
      1. stimulated by over stretched atria
      2. Increases water and sodium uptake to urine

         Nota:

         • = lowers blood volume
3. valves
   1. elastic fibres
   2. collagen
4. Epicardium

   Nota:

   • (visceral pericardium)
   1. fatty, loose connective tissue
      1. nerves
      2. vessels
      3. coronary arteries
      4. mesothelium
         1. simple cuboidal
         2. adipose tissue
5. Myocardium
   1. part which contracts
6. Endocardium
   1. endothelium
   2. loose connective tissue
   3. lots of Purkinje fibres