Blood Supply to The SKIN & its

lymphatic drainage.

Swetha. P

BLOOD SUPPLY TO THE SKIN

Contents

• Embryology

• Anatomy

• Physiological Functions

• Nerve supply

• Clinical Significance

EMBRYOLOGY • Angioblast- Form 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)

• 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.

ANATOMY

• VASCULAR ARCHITECTURE.

• HISTOLOGY.

• Anastomosis of superficial and deep vascular

plexusrich 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

• 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.

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

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

Histology of microvessels in reticular dermis. Large Arterioles

(A) can be distinguished from venules (V) by the presence of

elastic lamina which stains red.

SMALLER ARTERIOLES

• Absence of internal and external elastic

membrane

• Walls contain-Discontinued layer of

elastic fibres and smooth muscle

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).

PAPILLARY CAPILLARY LOOP

• ASCENDING ARTERIAL SEGMENT

• DESCENDING VENOUS SEGMENT

–Lumen Wider

–Numerous pericytes

–Multilayered basal lamina.

POST CAPILLARY VENULES

–Endothelial cells

–Pericytes

–Basal lamina

–Type III collagen fibres

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)

• 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

• BY ELECTRON MICROSCOPY,

Endothelial cell contains:

1. Cytoplamic filaments-7.5 -10nm

2. Pinocytic vesicles-50-70nm

3. Weibel-Palade bodies-Electron dense rod

shaped cytoplasmic structures

High-magnification view of Weibel–Palade bodies revealing

tubular profiles in cross-section.

CAPILLARIES:

1. 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.

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)

• 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

• 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

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.

• SUCQUET-HOYER CANAL:

–Single layer endothelium

–PAS positive, diastase resistant

basement membrane zone

–Media-4-6 layers of glomus cells

Glomus cells

• Modified smooth muscle cells

• Large cells with clear cytoplasm

• Uniform ovoid nucleus

• Innervated- unmyelinated adrenergic nerves

are present in the periphery.

Glomus cells surround arterioles and venules of

glomus bodies.

Physiological functions

• Nutritional support

• Immune surveillance

• Thermal regulation

• Wound healing

• Hemostasis

• Inflammation

Nerve Supply

• Controlled by adrenergic sympathetic nerves.

• These nerves are the efferent arm of

1. Baroreflex that originate in both arterial and

cardiopulmonary baroreceptors

2. Reflex baro response to upright posture and

exercise

3. Chemoreceptor reflex

4. Thermoregulatory reflexes

HUMORAL SUBSTANCES

• Direct effect upon arteriolar smooth muscle.

VASOCONSTRICTION VASODILATATION

Angiotensin II Histamine

Vasopressin Ethanol

Epinephrine Prostaglandin

Clinical significance

• Cutaneous capillary malformation-

– STURGE-WEBER SYNDROME-Seen in thelips,tongue,nasal and buccal mucosa

– Hereditary Hemorhhagic Telangiectasia

• Cutaneous vascular malformation-

- Klippel Trenaunay Syndrome

(Venous varicosities, edema, Hypertrophyof asssociated soft tissue and bone).

Contents

• Introduction.

• Histology.

• Physiological functions.

• Clinical significance.

• 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

• 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.

Superficial Dermis

Parallel structures to Vascular plexus.

Upper recticular Dermis

Single layer endothelium, discontinuous basal lamina

Deep part of dermis

Mesh Like

Subcutaneous fat

Single layer endothelium, discontinuous basal lamina, layers of smooth muscle cells

Lesser number of valves More number of valves

Increased lymphatic

clearence

Diminished lymphatic

clearence

Physiological functions

• Clearence of fluids, macromolecules,cells,

foreign materials from the interstitium.

• Maintains homeostasis.

Clinical significance

Failure of lymphatic system(burns, insect

bite,localisation of haematogenous

distribution infection) causes:

• Impaired immune function recurrent

infections.

• Lymphoedemas

• Fibrosis.

Summary

• BLOOD VESSEL.

1. Angioblast- Stem cells which forms the

endothelium, derived from the mesoderm.

2. Vascular architecture- Superficial and deep plexus,

connected to each other by communicating vessles.

3. From the superficial plexus, arises cascade of

capillaries that loops into each dermal papillae.

4. Anastomosis of superficial and deep plexus rich

through out the dermis.

5.HISTOLOGY-

Large arterioles & Arteries-

a. tunica intima- endothelium cells, int. elastic

membrane.

b. tunica media- Smooth muscle, external elastic

membrane

c. tunica adventitia- connective tissue.

Small arterioles-

a. absence of internal and external elastic membrane.

b. discontinuous smooth muscle & elastic fibres.

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.

Viel cells- flat adventitial cell, encircling

arterioles, capillaries & venules.

Endothelium Cell- cytoplasmic filaments,

pinocytic vescicles, Wiebel Palade bodies.

CapillariesContinous- lumina has cont. E.C,

transport – micropinocytotic vesicles

Fenestrated-transpor – intercellular gaps.

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.

9. Malformed cutaneous vascular– Klippel

trenaunay syndrome

10.Malformed capillaries –

Hereditary Hemorhhagic Telangiectasia

Sturge-Weber syndrome

• DERMAL LYMPHATICS

1. Upper part of reticular dermis, below superficial

plexus of venules.

2. Supported by elastic fibres & anchoring filaments.

3. Superficial lymphatics-Single layer endothelium,

discontinuous basal lamina.

4. Deep part of dermis-Single layer endothelium,

discontinuous basal lamina, layers of smooth

muscle cells.

• Function- clearence of fluid, macro mloecules,

foreign material & maintain homeostasis.

• Failure of lymphatic system- impaired

immune function, lymphoedemas.