Histology of Circulatory System Ii

Histology of Circulatory System Ii

HISTOLOGY OF CIRCULATORY SYSTEM II T- TUBULES & SARCOPLASMIC RETICULUM Less regular arrangement T- Tubules are more numerous At level of Z- line DIAD

CONDUCTING SYSTEM Mitochondria more numerous Lipofuscin pigment granules CARDIAC FIBROUS SKELETON Septum membranaceum Trigona fibrosa Annuli fibrosa



DIVISIONS MACROVASCULATURE: > 0.1m, large arterioles, muscular & elastic arteries, muscular veins MICROVASCULATURE: < 0.1m,

arterioles, capillaries, post capillary venules Exchange vessels TISSUE COMPONENTS Endothelium Muscular tissue Connective tissue (Elastic elements)

STRUCTURAL PLAN OF BLOOD VESSELS TUNICA INTIMA Endothelium Basal lamina Sub endothelial connective tissue Internal elastic lamina TUNICA MEDIA

Smooth muscles Elastic lamellae, reticular fibers Ground substance elements External elastic lamina TUNICA ADVENTITIA Collagen & elastic fibers VASA VASORUM

Vessels of vessels Arterioles, capillaries, venules in adventitia INNERVATION Sympathetic fibers (norepinephrine) Vasoconstriction Arteries in Skeletal Muscles- cholinergic

vasodilator fibers ENDOTHELIUM: Semi permeable barrier Monitor bidirectional exchange Nonthrombogenic surface; heparin, tissue plaminogen activator & Von Willibrand factor

Regulate Vascular tone & Blood flow; Contraction: endothelin 1 & ACE Relaxation: NO & Prostacyclin Inflammation & Local Immune response; Adhesion of WBCs, expression of P-Selectin, Weibel Palade Bodies

Growth Factors; VEGF in Vasculogenesis, Angiogenesis, role of Angiopoeitins Lipolysis Produce Vasoactive substances Thrombosis, emboli (Role of TPA)

VASCULAR SMOOTH MUSCLES Present in all vessels EXCEPT capillaries and post capillary venules Enclosed in basal lamina & connective tissue Arranged helically Connected by gap junctions

VASCULAR CONNECTIVE TISSUE Variable proportion Collagen, IV, III, I Elastic fibers Ground substance; heterogenous gel

Medical Application Arteriosclerosis Thickening of walls of small arteries Monkebergs calcific sclerosis Atherosclerosis LARGE ELASTIC ARTERIES T. INTIMA

Intima is thicker; smooth muscles in sub endothelial connective tissue Internal elastic lamina, though present not prominent T. MEDIA Concentric lamellae of elastic fibers (40-70) Reticular fibers, smooth muscles

T. ADVENTITIA Less developed Arterial Sensory Receptors Carotid & Aortic Sinus: Baroreceptors Tunica Media is thin--- allows distension Afferent impulses via 9th cranial nerve

Vasomotor center in brain Efferent adjust lumen to control BP Carotid & Aortic Bodies: Chemoreceptors Para ganglia with rich capillary network Glomus type I cells; dense core granules containing Dopamine, Ach

Supported by Satellite Type II cells Ion channels in Glomus cells respond to Low Oxygen, High CO2 or Acidosis Afferents to brain efferents to cvs or respiratory system MEDIUM SIZED, MUSCULAR ARTERIES T. INTIMA

Subendothelial layer thin Prominent internal elastic lamina T. MEDIA Smooth muscles- 40 layers Elastic fibers T. ADVENTITIA Connective tissue, vasa vasorum,

lymphatics SMALL ARTERIES & ARTERIOLES <0.5mm lumen Thin subendothelial connective tissue Int. elastic lamina absent in small arterioles T. Media: smooth muscle layer Adventitia is thin

Hypertension CAPILLARIES Diameter : 5-7 m Single layer of endothelium; permit metabolic exchange

Function in groups- Capillary Beds Richness conforms to metabolic activity of tissue Structure and pulsatile flow of blood through capillaries and thoroughfare channel. TYPES Continuous

Fenestrated Sinusoidal CONTINUOUS CAPILLARIES No fenestrations, complete basal lamina Pinocytic vesicles Location: Muscles, nervous tissue, exocrine glands

FENESTRATED CAPILLARIES Transcellular openings (80nm) Limited by cell membrane Covered by diaphragm ( thinner than cell membrane, proteoglycans) In endocrine glands

Kidneys etc SINUSOIDAL CAPILLARIES Diameter 30-40m Endothelial cells discontinuous layer Fenestrations without diaphragm Incomplete basal lamina Macrophages

Found in liver, hematopoietic organs PERICYTES Cells at periphery of continuous capillaries enclosed in own basal lamina Mesenchymal origin Actin, myosin contractile properties Role in repair process

Diabetic Microangiopathy

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