Blood vessels

Arteries

- Carry blood away from the heart.

Arterioles

Carry blood toward capillaries and regulate blood flow.

Capillaries

Exchange gases, nutrients, and wastes.

Venules

- Receive blood from capillaries.

Veins

Carry blood toward the heart.

Elastic arteries

Largest arteries; elastin stretches and recoils to dampen blood pressure surges. Example: aorta.

Muscular arteries

Thick tunica media distributes blood to organs. Example: brachial artery.

Arterioles

Smallest arteries; smooth muscle regulates capillary blood flow. Example: kidneys.

Tunica intima

Innermost tunic; contains simple squamous epithelium called endothelium.

Tunica media

Middle tunic; smooth muscle controls vessel diameter.

Tunica externa

Outermost tunic; connective tissue supports and protects the vessel.

Capillaries

Allow exchange of gases, nutrients, and wastes. Locations: lungs, small intestines, and kidney glomeruli.

Sinusoids

Wider, leakier capillaries that allow greater exchange. Locations: bone marrow and spleen.

Direct diffusion

Substances pass directly through endothelial cells.

Intercellular clefts

Small gaps between endothelial cells allow substances to pass.

Cytoplasmic vesicles

Transport substances through endothelial cells.

Fenestrations

Pores in endothelial cells that allow greater permeability.

Continuous capillaries

- Most common; tightly joined endothelial cells with small intercellular clefts.

Fenestrated capillaries

Have endothelial pores; found in intestines, kidney glomeruli, and endocrine glands.

Blood-brain barrier capillaries -

Have complete tight junctions and no intercellular clefts; selectively control substance passage.

Direct diffusion -

Substances pass directly through endothelial cells.

Intercellular clefts

Substances pass through small gaps between endothelial cells.

Cytoplasmic vesicles

- Transport substances through endothelial cells.

Fenestrations

Pores in endothelial cells allow substances to pass through.

Metarteriole

A vessel connecting an arteriole to a thoroughfare channel; has scattered smooth muscle cells.

Thoroughfare channel

A vessel that connects a metarteriole to a postcapillary venule, allowing blood to bypass the capillary network.

- Precapillary sphincter

A ring of smooth muscle at the entrance to a capillary that regulates blood flow into the capillary.

Capillaries

Smallest blood vessels; exchange gases, nutrients, and wastes.

Postcapillary venules

Receive blood from capillaries; have thin walls and allow white blood cells to leave the bloodstream and enter tissues.

Arteries

Thick walls, especially the tunica media; smaller, more circular lumen; maintain their shape.

Veins

Thinner walls, less smooth muscle in the tunica media, thicker tunica externa relative to the wall, and a larger, often irregular or collapsed lumen.

Vein valves

Prevent backflow and help blood return to the heart, especially against gravity.

Varicose veins

Enlarged, twisted veins caused by weakened vein walls or faulty valves that allow blood to pool.

Vascular anastomoses

Connections between blood vessels that provide alternate routes for blood flow if one route is blocked.

Vascular Anastomoses locations

Around joints, in the brain, and in the coronary circulation.

Vasa vasorum

Small blood vessels that supply oxygen and nutrients to the walls of large blood vessels.

Vasa vasorum location

Walls of the aorta and large veins, such as the venae cavae.

Superior vena cava

Returns deoxygenated blood from the upper body to the right atrium.

Inferior vena cava

Returns deoxygenated blood from the lower body to the right atrium

Pulmonary trunk

Carries deoxygenated blood from the right ventricle toward the lungs.

Pulmonary arteries

Carry deoxygenated blood to the lungs.

Pulmonary veins

Carry oxygenated blood from the lungs to the left atrium.

Aorta

Carries oxygenated blood from the left ventricle to the body.

Right atrium

Receives deoxygenated blood from the venae cavae.

Tricuspid valve

Allows blood to flow into the right ventricle.

Right ventricle

Pumps blood through the pulmonary semilunar valve into the pulmonary trunk.

Pulmonary semilunar valve

Prevents blood from flowing back into the right ventricle.

Left atrium

Receives oxygenated blood from the pulmonary veins.

Mitral (bicuspid) valve

Allows blood to flow into the left ventricle.

Left ventricle

Pumps blood through the aortic semilunar valve into the aorta.

Aortic semilunar valve

Prevents blood from flowing back into the left ventricle.

Pulmonary circulation

Movement of blood from the right ventricle to the lungs for gas exchange and back to the left atrium.

Pulmonary trunk

Carries deoxygenated blood from the right ventricle.

Right and left pulmonary arteries

Carry blood to the respective lungs.

Pulmonary capillaries

Allow carbon dioxide to leave the blood and oxygen to enter.

Pulmonary veins

Return oxygenated blood to the left atrium.

Trace a Drop of Blood from the Pulmonary Trunk to the Left Atrium

Pulmonary trunk → right or left pulmonary artery → smaller arteries and arterioles → pulmonary capillaries around the alveoli → venules → pulmonary veins → left atrium.

Why Pulmonary Arteries Are Blue

Carry deoxygenated blood, which has less oxygen.

Why Pulmonary Arteries Are red

- Carry oxygenated blood, which has more oxygen.

Aorta

Main artery supplying the body through its branches.

Coronary arteries

Heart muscle.

Brachiocephalic trunk

Right head, neck, and upper limb.

Common carotid arteries

Head and neck.

Vertebral arteries

Brain and spinal cord.

Subclavian arteries

Upper limbs.

Axillary arteries

Armpit and shoulder region.

Brachial arteries

- Upper arms.

Radial and ulnar arteries

Forearms and hands.

Celiac trunk

Stomach, liver, spleen, and upper digestive organs.

Superior mesenteric arter

Most of the small intestine and part of the large intestine.

Renal arteries

Kidneys.

Gonadal arteries

Ovaries or testes.

Inferior mesenteric artery

Distal large intestine, including the descending and sigmoid colon and upper rectum.

Common iliac arteries

Pelvis and lower limbs through their branches.

Femoral arteries

Thighs.

Popliteal arteries

Knee region.

Anterior and posterior tibial arteries

Lower legs and feet.

Fibular arteries

Lateral lower legs.

Brachiocephalic veins - What do they drain?

Brachiocephalic veins - What do they drain? The head, neck, upper limbs, and upper chest.

Internal jugular veins - What do they drain?

The brain and deep head and neck.

External jugular veins - What do they drain?

The superficial head and neck.

Subclavian veins - What do they drain?

The upper limbs.

Axillary veins - What do they drain?

The armpit and shoulder.

Brachial veins - What do they drain?

The upper arms

Radial and ulnar veins - What do they drain?

The forearms and hands.

Azygos vein - What does it drain?

The thoracic wall.

Common iliac veins - What do they drain?

The pelvis and lower limbs.

Internal iliac veins - What do they drain?

The pelvic organs and walls.

External iliac veins - What do they drain?

The lower limbs.

Femoral veins - What do they drain?

The thighs.

Popliteal veins - What do they drain?

The knee region.

Anterior and posterior tibial veins - What do they drain?

The lower legs and feet.

Renal veins - What do they drain?

The kidneys.

Gonadal veins - What do they drain?

The ovaries or testes.

Hepatic veins - What do they drain?

The liver.

Lumbar veins - What do they drain?

The posterior abdominal wall.

Inferior phrenic veins What do they drain?

The diaphragm.

• Gastric veins - What do they drain?

The stomach.

Superior mesenteric vein What does it drain?

Most of the small intestine, cecum, ascending colon, and part of the transverse colon.

Inferior mesenteric vein - What does it drain?

The descending and sigmoid colon and upper rectum.