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
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.
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
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)
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.
Smooth muscle layers: Fenestrated elastic sheets/laminae (elastic arteries), External elastic lamina (EEL, where applicable)
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.
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.
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.
Master gene required for the formation and development of the primary heart field
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
1. Cardiac myoblasts 2. Angioblasts
PHF cells induced to form
(initially 2-fuse to form 1), Blood from heart to body, YS, Placenta
Secreted by neural tube, inhibitory to cardiogenesis.
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).
Structures remain open or partially open past the normal range of closure times
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)
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.
Important in expression of cardiac specific proteins.
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
Left sinus horn becomes
Bypasses liver directly to the Inferior Vena Cava (IVC)
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
Formation of heart valves is completed.
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.
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.
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):
- Blood coagulation & thrombus (clot) formation
- Inflammatory reactions - Fluid movement into tissues, WBC migration into tissues