VESSELSVESSELSgeneral overviewgeneral overview

• tunica intima

• subedothelial layer of connective tissue

• membrana elastica interna

• tunica media

• membrana elastica externa

• tunica adventitia = tunica externa

GENERAL STRUCTURE OF VASCULAR WALLGENERAL STRUCTURE OF VASCULAR WALL

General structure of vascular wallGeneral structure of vascular wall

• tunica intima

• tunica media

• tunica adventitia

(externa)

Tunica intimaTunica intima

• endothelial cells (endotheliocyti)– simple flat/squamous epithelium– on basal lamina

• subendothelial layer (stratum subendotheliale)– loose connective tissue– some smooth muscle cells

• lamina elastica interna – elastin

Endothelial cells (Endothelial cells (EndotheliocytiEndotheliocyti))

• mesenchymal origin• zonulae occludentes, desmosomes, nexuses• intermediate filaments, microfilaments (contraction)• corpora multitubularia (Weibel-Palade‘s bodies)

• f. VIII – vWF, P-selectin• receptors: adrenergic, histaminic, ADH• synthesis of vasoactive substances: NO, PG

Tunica mediaTunica media

• smooth muscle cells– spiral arrangement

• elastic a collagen fibers (type III)

• lamina elastica externa– only in thicker arteries

Tunica adventitia (externa)Tunica adventitia (externa)

• fibroblasts

• collagen fibers (type I)

• elastic fibers

• vasa vasorum

• nervi vasorum

Vessel typesVessel types• arteries (arteriae) - aer + térein

– muscular x elastic x mixed– microcirculation: small arteries – less than 1 mm– arterioles (arteriolae)

• less than 100 μm• several layers of smooth muscle cells• principal source of peripheral resistance !!!

– metarterioly• one smooth muscle cell layer, precapillary sphincter

• capillaries (vasa capillaria)– no nerve fibers– endotheliocyte + pericyte (Rouget‘ s cell)– caliber ± 7 μm

Vessel typesVessel types

• veins (venae)– few muscle cells, more valvules– venules (venulae)

• capacity part of circulation (70% of blood)

• lymph vessels (vasa lymphatica)– lymph capillaries (vasa lymphocapillaria)

• originate as cul-de-sac

– lymphatic trunks and ducts (trunci et ductus lymphatici)

• collectors in limbs• valvules

Elastic arteriesElastic arteriesaorta, truncus pulmonalis, a. subclavia, axillaris, iliaca, femoralis, thoracica int.

Elastic arteryElastic artery((Arteria elastotypica)Arteria elastotypica)

• Tunica intima– lamina elastica interna – incoherent

• Tunica media– elastic membranes with fenestrations – elastin – smooth muscle cells– lamina elastica externa

• Tunica adventitia (externa)– frequent vasa vasorum

• supply outer 2/3 of wall

Elastic artery (van Gieson + elastin)

Elastic artery (elastin)

Muscular artery (Muscular artery (arteria musculotypica)arteria musculotypica)

• Tunica intima– thin– lamina elastica interna – obvious

• Tunica media– circular smooth muscle cell layer (up to 40 layerss)

• each cell is covered with basal lamina – communication• synthesis of extracellular matrix

– lamina elastica externa – several elastic membranes

• Tunica externa– nerve bundles – contraction

Muscular arteryMuscular artery (HE) (van Gieson + elastin)

Arterioles = Arterioles = ArteriolaeArteriolae caliber < 0.5 mm

• Tunica intima– Weibel-Palade‘ s bodies within endothelail cells

(not in capillaries!)– lamina elastica int. – absent in smallest arterioles

• Tunica media– 1-3 layers of smooth muscle cells– lamina elastica ext. – absent

• Tunica adventitia (externa) – very thin

principal source of peripheral resistance

ArteriolaArteriola (HE)

ArteriolaArteriola (HE)

SensorySensory structures in arteriesstructures in arteries

• Glomera supracardiaca (aortica) – sup., medium, inf. - baroreceptors

• Sinus caroticus - baroreceptor– thicker, richly innervated tunica adventitia– thinner tunica media

• Glomus caroticum - chemoreceptors– oval structures - 3-5 mm

• glomus cells – large nucleus, vesicles with catecholamines• shield cells – cover neural endings as glia

Capillaries (Capillaries (Vasa capillariaVasa capillaria))

• microvascular part of circulation– vas capillare arteriale, intemredium, venosum– site of gas and nutrients exchange

• capillary– caliber 7-9 μm– length 1 mm (50 mm in renal glomerulus)– total length approximately 96 000 km– formed by endothelial cells on basal lamina

Capillaries – Capillaries – wall structureswall structures

• Endothelial cell (Endothelicytus)

• Basal lamina (Lamina basalis)

• Pericyte (Pericytus; Rouget‘s cells)– mesenchymal cells with long processes– stem, supporting and transporting cell– proper lamina basalis– contractile proteins (replaces tunica media)

Capillary bed(HE)

Capillary typesCapillary types• somatic capillaries

– muscle, conncetive tissue, exocrinne glands (pinocytar vesicle in the wall), nervous tissue (no vesicles)

• fenestrated (visceral) capillaries with diaphragms– fenestrations 60-80 nm (quick metabolic exchange)– kidneys, gut, endocrinne glands

• fenestrated capillaries without diaphragms– glomeruli in kidney

• sinusoids– caliber 30-40 μm, often without lamina basalis– hematopoetic organs – liver, spleen, bone marrow, dental

pulp

• glomus, glomi n. (vessel glomerule) – ball of fingers, nailbeds, auricle, penis / clitoris, uterus

Capillaries -Capillaries - functionfunction• permeability

– exchanger vessels (diffusion, pores, fenestration, vesicles)

• metabolic function– activation of angiotensin I angiotensin II

(lungs)– inactivation of bradykinin, serotonin,

prostaglandins– lipolysis

• antithrombotic function– inhibition of tissue thromboplastin

Somatic capillarySomatic capillary (EG)

Somatic capillary Somatic capillary (EG)

Fenestrated capillary Fenestrated capillary (EG)

Fenestrated capillary Fenestrated capillary (EG)

Other structures of vascular wallOther structures of vascular wall

• vasa vasorum

• vasa nervorum

• nervi vasorum

Other peculiar vascular structuresOther peculiar vascular structures

• vas anastomoticum (anastomosis)• vas collaterale (collateral)• rete mirabile = portal system

– 2 capillary beds series-connected

• anastomosis arteriovenosa (arteriolovenularis) – endothel bulges of intimal cushions with

myoepitheloid cells• simple (skin, lungs, kidneys)• composed (glomus coccygeum)

Vessel network arrangementVessel network arrangement

• terminal (retina, spleen, kidney)

• functionally terminal (heart, brain)

• anastomotic

angiogenesis – hypoxia is the strongest factor !

Clinical relevanceClinical relevance

• aneurysma

• atherosclerosis (athere + skleros)

• necrosis, infarctus

• air embolism in large cervical veins

• varices

Blood distribution in organsBlood distribution in organs

• heart (coronary arteries) 5%

• brain 15%

• muscles 15%

• viscera 35%

• kidneys 20%

• skin, skeleton 10%

according to Stingl

Development of arterial systemDevelopment of arterial system

Developmental arteriesDevelopmental arteries• Saccus aorticus (aortal sac)• Aa. arcuum pharyngeorum (pharyngeal arch

arteries; „aortal arches“)– 5 pairs develop and change successively

• Aorta dorsalis (original 2 merge into 1)– a.a segmentales ventrales ( a. omphalomesenterica,

unpaired branches from AA)– truncus umbilicalis ( a. iliaca communis + int.)– a. umbilicalis– aa. segmentales laterales ( paired branches from AA)– aa. intersegmentales dorsolaterales ( branches from a.

subclavia)– a. sacralis mediana

Day 20-22

Pharyngeal arch arteries derivatesPharyngeal arch arteries derivates• 1st pair – arteria maxillaris + carotis externa• 2nd pair – arteria stapedia • 3rd pair – central – arteria carotis communis

– peripheral – arteria carotis interna

Pharyngeal arch arteries derivatesPharyngeal arch arteries derivates• 4th pair

– left – part of the arcus aortae– right – a. subclavia dx.

• peripheral part of a. subclavia dx. is derived from aorta dorsalis dextra

– a. subclavia sin. is NOT derived from the 4th aortic arch but from 7th intersegmental artery

Pharyngeal arch arteries derivatesPharyngeal arch arteries derivates• 5th – Ø• 6th pair

– left central left pulmonary artery

peripheral ductus arteriosus (Botali)– right central right pulmonary artery

peripheral Ø

Arteriae omphalomesentericaeArteriae omphalomesentericae(vitellinae)(vitellinae)

• number of paired arteries• supply yolk sac• develop in vascular supply of gut → truncus

coeliacus, arteria mesenterica superior et inferior

Arteriae umbilicalesArteriae umbilicales• paired branches

– central: truncus umbilicalis from aorta dorsalis– peripheral: within mass of diverticulum allantoicum

• to placenta (originally to allantois) in embryonic (connective) stalk or later in umbilical cord

• persist as arteriae iliacae internae and vesicales superiores – central: pars patens)– peripheral: ligamentum umbilicale mediale = pars

occlusa

Malformation of arteriesMalformation of arteries

• Ductus arteriosus patens

• Coarctatio aortae

• Arcus aortae duplex

• Arcus aortae dexter

• Arteria lusoria– abnormal origin of the right subclavian artery –

obliteration of right aortic arch – origin of 7th segmental artery

Malformation of arteriesMalformation of arteries

• course changes

• clinically relevant:– a. radialis

• a. brachioradialis (14%)

– a. ulnaris• a. brachioulnaris superficialis (3%)

Development of venous systemDevelopment of venous system

Developmental veinsDevelopmental veinsvv. somaticae• v. cardinalis communis = ductus Cuvieri• v. precardinalis ( v. jugularis int.+ ext.)• v. postcardinalis ( v. azygos + hemiazygos)• anastomosis subcardinalis

– vv. subcardinales

• vv. intersegmentales – v. marginalis membri + v. axialis m.s./m.i.( vv. subclaviae + superficial and deep limb veins)

vv. viscerales• vv. omphalomesentericae (vitellinae)• v. umbilicalis (originally 2, right one disappears)• v. pulmonalis communis

Vena cava inferiorVena cava inferior

• v. omphalomesenterica intraembryonica pars hepatica VCI

• anastomosis subcardinalis + v. subcardinalis dx. pars subcardinalis VCI

• developmental anomalies 1-2%– infrarenal duplication

Vena portaeVena portae

• vv. omphalomesentericae intraembryonicae

• vv. afferentes hepatis

• ductus venosus lig. venosum)

• vv. efferentes hepatis vv. hepaticae

Vena portae Vena portae preduodenalispreduodenalis

rare