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Flashcards in Histology - Vasculature Deck (70)

Medium size, continuous basal lamina, have small openings through plasma membrane that may or may not be closed by a diaphragm. Found in endocrine organs, GI tract, and kidney.

Fenestrated (type II) Capillaries


Most external layer composed of fibroelastic connective tissue that is continuous with and blends into CT. Contains ANS postganglionic nerve fibers that innervate the smooth muscle cells in the TM and vasa vasorum for nutrients.

tunica adventitia (TA)


Initially left and right associated with arch 6, but when arch 6 is lost from the right side, it 'slides' up to arch 4, while arch 6 remains in place (ductus arterosus).

Recurrent laryngeal nerve fetal development


Secreted by endoderm & visceral mesoderm, upregulates expression of FGF8 gene

BMP 2, 4


Directly controls amount of blood flow through capillary beds

Precapillary sphincter


a small ligament attached to the superior surface of the left pulmonary artery and the proximal descending aorta. a nonfunctional vestige of the ductus arteriosus, and is formed within three weeks of birth.

ligamentum arteriosum


L ventricle to left atrium -> foramen ovale to right atrium -> to right ventricle to pulmonary trunk -> DUCTUS ARTERIOSUS

Compensatory blood flow (prenatal) in preductal constriction of the aorta


right sinus horn

upper part of the IVC fetal derivative


6-8 microns in diameter (smallest), found in tightest tight junctions, prominent pinocytotic vesicles. Continuous and complete basal lamina, found everywhere.

Continuous (type I) capillary


Tunica media: 5-40 layers smooth muscle arranged in a spiral fashion. Prominent IEL & EEL.

Muscular (distributing) arteries


(1) SVC (2) upper part of the IVC (3) incorporated into the right atrium (smooth part)

Right sinus horn becomes


Subclavian aa -> Internal thoracic arteries -> Anterior intercostal -> arteries -> Posterior intercostal arteries -> Thoracic aorta (to lower body & Les)

Postductal coarctation of the Aorta collateral circulation


Partitioning of the heart into 4 chambers begins.

Week 5 Heart Development


a collection of veins joined together to form a large vessel that collects blood from the heart muscle

coronary sinus


1. Enlargement of collateral arteries. 2. X-ray: Notching of ribs (on posterior 1/3). 3. Despite compensation, blood pressure in UEs much higher than in LEs

Postductal coarctation of the Aorta presentation


Thin tunica intima & adventita. Tunica media made of 1-4 layers smooth muscle. May have IEL but no EEL. They control blood flow into capillary beds by increasing or decreasing lumen diameter (thereby or vascular resistance to blood flow). They are the principal control of systemic blood pressure



Aortic arches undergo primary changes to adult form.

Week 6 Heart Development


common cardinal vein, Umbilical vein, Vitelline vein

intial sinus horn inflow


Endothelium: Weibel-Palade bodies, Subendothelial connective tissue (CT) layer, Internal elastic lamina (IEL, where applicable)

Tunica intima


Wedge-shaped portion of aortic arch, Ductus arteriosus (ligamentum arteriosum)

Aortic arches become…


Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbed from 1 to 6, with 1 being the closest to the head of the embryo, and 5 existing only transiently. They develop during the fourth week crainal to caudal on both sides of the developing pharynx.

Aortic and associated pharyngeal arches


1. Endothelial cell regrowth (from uninjured areas) 2. Smooth muscle cell migration into the tunica intima. 3. Smooth muscle cell proliferation. 4. Smooth muscle cell secretion of ECM.

Vascular injury associated with endothelial cells loss or dysfunction results in…


a depression in the right atrium of the heart, the remnant of a thin fibrous sheet that covered the foramen ovale during fetal development.

fossa ovalis


Smooth muscle layers: Fenestrated elastic sheets/laminae (elastic arteries), External elastic lamina (EEL, where applicable)

Tunica media


contractile cell located within endothelial basal lamina that communicate with endothelial cell via gap junctions that are ctivated with injury & during wound healing. They are mesenchymal –type cells tha can act as stem cell and give rise to: endothelial cells & smooth muscle cells during angiogenesis.

Pericytes (Rouget cells)


Relatively wide, irregular lumen, thinner walls, valves and no internal elastic lamina.

Medium vein (MV)


Arranged in networks. Consist of endothelial cells, basal lamina, and pericytes.



Blood flow into the right atrium from the IVC to the left atrium, bypassing pulmonary circulation.

Foramen ovale


are the nerves of the sixth pharyngeal arch, right and left that emerge from the vagus nerve at the level of the arch of aorta, and then travel up the side of the trachea to the larynx.

Recurrent laryngeal nerve


Constriction distal to ductus ateriosus. Separation of arterial circulation of Head/Upper trunk/UE from that of the Lower trunk/LEs that cannot be compensated for by the ductus arteriosus. Before birth have to develop extensive collateral circulation to bypass the narrowed aortic region and supply the lower trunk/LEs.

Postductal coarctation of the aorta


Continuous (type I), Fenestrated (type II), Sinusoidal (or discontinuous)

types of capillaries


Modified cardiac muscle fibers, located in subendoCARDial, (not epithelial). Large pale-looking (“moth-eaten) cells.

Purkinje Fibers


Function: Regulation of regional blood flow (distribution). Examples: Axillary artery, Internal thoracic artery, Intercostal arteries

Muscular (distributing) arteries examples and functions


Relatively small, regularly shaped lumen, thick walls with internal elastic lamina

Muscular artery (MA)


The lungs are not oxygenating fetal blood. They need just enough blood to sustain.

Pulmonary bypass


Master gene required for the formation and development of the primary heart field



Tunica intima

Site of Atherosclerotic Plaque Formation


Blood to/from fetus to/from yolk sac

Vitelline arteries and arteries


sprouting of new vessels from existing vessels



Large irregular lumen. Discontinuous basal lamina. Found in Bone marrow, liver, spleen (sites of fluid & cell migration in & out of BV).

Sinusoidal (discontinuous) capillary


NKX-2.5 expression in visceral mesoderm (PHF)

BMPs + C & C cause


Venous blood from fetus back to heart

Cardinal veins


1. Cardiac myoblasts 2. Angioblasts

PHF cells induced to form


(initially 2-fuse to form 1), Blood from heart to body, YS, Placenta

Dorsal aorta


Secreted by neural tube, inhibitory to cardiogenesis.

WNT proteins


the fibrous remnant of the ductus venosus of the fetal circulation. Usually, it is attached to the left branch of the portal vein within the porta hepatis (gateway to the liver).

ligamentum venosum


Structures remain open or partially open past the normal range of closure times

Fetal Patency


Functions: 1. Expand during systole & recoil during diastole 2. Propel blood along blood vessel system. Examples: Pulmonary trunk, Aorta (all parts), Brachiocephalic trunk, Common carotid arteries, Subclavian arteries

Elastic (conducting) arteries functions and examples


Ductus Venous. Oxygenated blood in the umbilical vein does not need to be filtered by the fetal liver (placenta has done that job)

Liver bypass


a blood vessel connecting the pulmonary artery to the proximal descending aorta, allowing most of the blood from the right ventricle to bypass the fetal lungs.

Ductus Arteriosus


Important in expression of cardiac specific proteins.

FGF8 gene


Heart and embryonic blood vessels begin to develop. Embryonic circulation established. Heart begins to beat. Cardiac lopping completed.

Weeks 3 + 4 Heart Development


Umbilical vein (Placenta, Ox), Vitelline veins (YS, de-Ox), Cardinal veins (Body, de-Ox)

Fetal inflow to heart


Aortic arches: Head & Neck, Dorsal aorta: Body; YS: Vitelline a; Placenta: Umbilical aa

Outflow from heart


coronary sinus

Left sinus horn becomes


Bypasses liver directly to the Inferior Vena Cava (IVC)

Ductus venosus


Lateral Plate Mesoderm - Visceral Layer

Heart Embryonic Germ Layer


a “horseshoe-shaped” cluster of cells cranial (& lateral) to the neural folds developed early in week 3.

Primary heart field (PHF)


Specializations of the Endocardium (Tunica Intima). Extensions of fibroelastic tissue deep to endothelium. Covered on luminal surfaces by endothelium

Cardiac Valves


Formation of heart valves is completed.

Week 8


Functions: Transport blood to large veins (may have valves) Examples: Axillary vein, Internal thoracic veins, Intercostal veins, Cardiac veins (heart)

Medium veins examples and functions


At birth: 1. Head, upper trunk & UEs have normal color 2. Lower trunk & LEs are cyanotic (blue).

Preductal coarctation of the aorta presentation


First venules after the capillary bed, consisting of endothelial lining, basal lamina , pericytes (stem cells). Site of fluid movement and leukocyte extravasation.

Postcapillary Venules


Secreted by endoderm, blocks WNT

crescent & cerberus


Organs of the body, Connective tissues, Smooth & cardiac muscle, Circulatory system (blood & lymphatic vessels)

Visceral (splanchnic) mesoderm derivatives


a vein running up the right side of the thoracic vertebral column. It can also provide an alternative path for blood to the right atriumby allowing the blood to flow between the venae cavae when one vena cava is blocked.

Azygos vein


platelet adhesion at an injury site, secreted directly into the underlying subendothelial CT layer or stored within the endothelial cell cytoplasm in electron dense secretory vesicles.

Willebrand factor (vWF)


Prostaglandin E2 administration to keep ductus open until repair can be done.

Treatment for constriction of the aorta


Constriction just proximal to ductus ateriosus, blood flow to head/neck & UEs is OK, but blood to lower body affected. Is compensated for via an alternative pathway through ductus arteriosus.

Preductal constriction of the aorta


Endothelium: General Functions

Barrier, Exchange Functions: 

Paracellular and Transcellular Transport - Tight junctions, Basal lamina, Gap junctions (exchange between endothelial cells)

Synthetic & Secretory (affects):

  1. Blood coagulation & thrombus (clot) formation
  2. Inflammatory reactions - Fluid movement into tissues, WBC migration into tissues
  3. Angiogenesis