Blood supply and lymphatics of skin

Blood supply & lymphatics of skin

1. Blood Supply to The SKIN & its lymphatic drainage. Swetha . P

2. BLOOD SUPPLY TO THE SKIN

3. Contents Embryology Anatomy Physiological Functions Nerve supply Clinical Significance

4. EMBRYOLOGY Angioblas t - F orm small cell clusters [Blood islands] within embryonic and extra embryonic mesoderm. These blood islands extend and fuse  Primordial vascular network Within these islands  Peripheral cells Endothelial cell Core cells Blood cells ( haemocytoblasts )

5. Formation of the initial endothelial tube is by a process of coalescence of cellular vacuoles within the developing endothelial cells. The vacuoles fuse together without cytoplasmic mixing to form the blood vessel lumen.

6. ANATOMY VASCULAR ARCHITECTURE. HISTOLOGY.

7. Anastomosis of superficial and deep vascular plexus rich throughout the dermis Developed at the level of upper dermis and around folliculo -sebaceous apocrine units and eccrine glands This arrangement permits preferential blood flow in alternative channels if other routes-blocked

8. Histo -chemical detection of alkaline phosphatase activity indicates the presence of arborizing nature of cutaneous circulation. Numerous capillaries in the adventitial dermis, here shown enveloping sebaceous and eccrine glands.

9. HISTOLOGY Arteries in subcutaneous fat and large arterioles(deep part of dermis) Smaller arterioles(Superficial dermis) Papillary capillary loop  Ascending arterial segment . Descending venous segment Post capillary venules Large venules and vein

10. Arteries in subcutaneous fat and large arterioles TUNICA INTIMA- Endothelial cell , internal elastic membrane TUNICA MEDIA- Collagen ,non layered elastic fibres , smooth muscles TUNICA ADVENTITIA: Elastic fibres,type III collagen , fibrocytes

11. Histology of microvessels in reticular dermis. Large Arterioles (A) can be distinguished from venules (V) by the presence of elastic lamina which stains red.

12. SMALLER ARTERIOLES Absence of internal and external elastic membrane Walls contain-Discontinued layer of elastic fibres and smooth muscle

13. Transmission E.M of cross-section through a small arteriole . Endothelial cell (E) surrounding the lumen (L) and the presence of smooth muscle ( SM).Small amount of elastic tissue (el) next to the endothelial basement membrane ( bm ).

14. PAPILLARY CAPILLARY LOOP ASCENDING ARTERIAL SEGMENT

15. DESCENDING VENOUS SEGMENT Lumen  Wider Numerous pericytes Multilayered basal lamina.

16. POST CAPILLARY VENULES Endothelial cells Pericytes Basal lamina Type III collagen fibres

17. T.E.M of a transverse section through a venule .Endothelial cells (E) in the lumen (L) is more convoluted. The endothelial cells are surrounded by pericytes (P), and not smooth muscle cells, and the basement membrane ( bm )

18. LARGER VENULES AND VEINS Variable amount of smooth muscle and elastic fibres No elastic membrane Valves VEIL CELLS Flat adventitial cells encircling arterioles,capillaries and venules Demarcates the vessel wall from surrounding dermis

19. BY ELECTRON MICROSCOPY, Endothelial cell contains: Cytoplamic filaments-7.5 -10nm Pinocytic vesicles-50-70nm Weibel -Palade bodies-Electron dense rod shaped cytoplasmic structures

20. High-magnification view of Weibel –Palade bodies revealing tubular profiles in cross-section.

21. CAPILLARIES: TYPES : Continuous and fenestrated CONTINUOUS: Lumina - continuous circumferential layer of endothelial cells. Specialized intracellular junctions. Exchange of fluid and small water soluble molecules –Via within micropinocytotic vesicles.

22. Cross section through a capillary . Part of five endothelial cells are pictured(E,E’),Basement membrane is seen surounding and pericyte (P).within the lumen (L) is a platelet (Pl)

23. FENESTRATED VENOUS CAPILLARIES : Situated –Adventitial dermis. (Adjacent to eccrine glands and follicular bulbs) Permits passage of large molecules (plasma proteins) Intracellular gaps-Widened by contraction of Actin filaments

24. Through these permeable walls of capillary and venules : O2,water,nutrients and hormones-Delivered from blood stream to tissues CO2,metabolic byproducts- transported to excretory organs

25. Glomus bodies Specialized arterio -venous shunts Most abundant in recticular dermis of acral skin Regulation of temperature. Arterial segment- Sucquet Hoyer canal. - Narrow lumen, thick wall -endothelium,3-6 rows of glomus cells. Venous segment- thin wall - wide lumen.

26. SUCQUET-HOYER CANAL: Single layer endothelium PAS positive, diastase resistant basement membrane zone Media-4-6 layers of glomus cells

27. Glomus cells Modified smooth muscle cells Large cells with clear cytoplasm Uniform ovoid nucleus Innervated- unmyelinated adrenergic nerves are present in the periphery.

28. Glomus cells surround arterioles and venules of glomus bodies.

29. Physiological functions Nutritional support Immune surveillance Thermal regulation Wound healing Hemostasis Inflammation

30. Nerve Supply Controlled by adrenergic sympathetic nerves. These nerves are the efferent arm of Baroreflex that originate in both arterial and cardiopulmonary baroreceptors Reflex baro response to upright posture and exercise Chemoreceptor reflex Thermoregulatory reflexes

31. HUMORAL SUBSTANCES Direct effect upon arteriolar smooth muscle. VASOCONSTRICTION VASODILATATION Angiotensin II Histamine Vasopressin Ethanol Epinephrine Prostaglandin

32. Clinical significance Cutaneous capillary malformation- STURGE-WEBER SYNDROME-Seen in the lips,tongue,nasal and buccal mucosa Hereditary Hemorhhagic Telangiectasia Cutaneous vascular malformation- - Klippel T renaunay Syndrome (Venous varicosities, edema, Hypertrophy of asssociated soft tissue and bone).

33. Contents Introduction. Histology. Physiological functions. Clinical significance.

34. Parallel to the major vascular network. Walls are not well developed. From superficial plexus of lymphatic capillaries  thicker walled lymphatic vessels with Valves  venous circulation. introduction

35. SITE:- Upper part – recticular dermis Below the superficial plexus of venules At the zone - orientation of elastic fibres changes from vertical – horizontal Supported by elastic fibers & anchoring filaments.

36. Lesser number of valves More number of valves Increased lymphatic clearence Diminished lymphatic clearence

37. Physiological functions Clearence of fluids, macromolecules,cells , foreign materials from the interstitium . Maintains homeostasis.

38. Clinical significance Failure of lymphatic system(burns, insect bite,localisation of haematogenous distribution infection) causes: Impaired immune function  recurrent infections. Lymphoedemas Fibrosis.

39. Summary BLOOD VESSEL. Angioblast - Stem cells which forms the endothelium, derived from the mesoderm. Vascular architecture- Superficial and deep plexus, connected to each other by communicating vessles . From the superficial plexus, arises cascade of capillaries that loops into each dermal papillae. Anastomosis of superficial and deep plexus rich through out the dermis.

40. 5.HISTOLOGY- Large arterioles & Arteries- tunica intima- endothelium cells, int. elastic membrane. tunica media- Smooth muscle, external elastic membrane tunica adventitia- connective tissue. Small arterioles- absence of internal and external elastic membrane. discontinuous smooth muscle & elastic fibres .

41. Ascending arterial limb- epithelial cell, pericytes , basement membrane . Descending venous segment- epithelial cells, with numerous pericytes , multilayered basal lamina . Post Capillary venule - epithelial cells, basement membrane, collagen fibres . Large venules & vein- variable amount of smooth muscle, No ELASTIC Membrane.

42. Viel cells- flat adventitial cell, encircling arterioles, capillaries & venules . Endothelium Cell- cytoplasmic filaments, pinocytic vescicles , Wiebel Palade bodies. Capillaries Continous - lumina has cont. E.C, transport – micropinocytotic vesicles Fenestrated- transpor – intercellular gaps.

43. 6.Glomus bodies - specialised A-V shunts with out interposition capillaries. -regulation of temperature . 7.Functions - nutritional support, immune survielence , thermal regulation, wound healing, hemostasis, inflamation . 8.They are supplied by adrenergic sympathetic nerves.

44. 9 . Malformed cutaneous vascular– Klippel trenaunay syndrome 10.Malformed capillaries – Hereditary Hemorhhagic Telangiectasia Sturge -Weber syndrome

45. DERMAL LYMPHATICS Upper part of reticular dermis, below superficial plexus of venules . Supported by elastic fibres & anchoring filaments . Superficial lymphatics -Single layer endothelium, discontinuous basal lamina. Deep part of dermis-Single layer endothelium, discontinuous basal lamina, layers of smooth muscle cells.

46. Function- clearence of fluid, macro mloecules , foreign material & maintain homeostasis . Failure of lymphatic system- impaired immune function, lymphoedemas .