Blood vessel

Simple diagram of the human circulatory system
Transmission electron micrograph of a blood vessel displaying an erythrocyte (red blood cell, E) within its lumen, endothelial cells forming its tunica intima (inner layer), and pericytes forming its tunica adventitia (outer layer).
Diagram of blood vessel structures
Constricted blood vessel.

The blood vessels are the components of the circulatory system that transport blood throughout the human body.

- Blood vessel
Simple diagram of the human circulatory system

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Types of epithelium

Epithelium

One of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue.

One of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue.

Types of epithelium
Summary showing different epithelial cells/tissues and their characteristics.
Forms of secretion in glandular tissue
Different characteristics of glands of the body
Epithelial cell infected with ''Chlamydia pneumoniae
Squamous epithelium 100x
Human cheek cells (Nonkeratinized stratified squamous epithelium) 500x
Histology of female urethra showing transitional epithelium
Histology of sweat gland showing stratified cuboidal epithelium

Epithelial tissues line the outer surfaces of organs and blood vessels throughout the body, as well as the inner surfaces of cavities in many internal organs.

The human circulatory system (simplified). Red indicates oxygenated blood carried in arteries. Blue indicates deoxygenated blood carried in veins. Capillaries join the arteries and veins.

Circulatory system

Several terms redirect here.

Several terms redirect here.

The human circulatory system (simplified). Red indicates oxygenated blood carried in arteries. Blue indicates deoxygenated blood carried in veins. Capillaries join the arteries and veins.
Blood flow in the pulmonary and systemic circulations showing capillary networks in the torso sections
Diagram of the human heart viewed from the front
The pulmonary circulation as it passes from the heart. Showing both the pulmonary and bronchial arteries.
Capillary bed
Diagram of capillary network joining the arterial system with the venous system.
Depiction of the heart, major veins and arteries constructed from body scans
Animation of a typical human red blood cell cycle in the circulatory system. This animation occurs at a faster rate (~20 seconds of the average 60-second cycle) and shows the red blood cell deforming as it enters capillaries, as well as the bars changing color as the cell alternates in states of oxygenation along the circulatory system.
Magnetic resonance angiography of aberrant subclavian artery
The open circulatory system of the grasshopper – made up of a heart, vessels and hemolymph. The hemolymph is pumped through the heart, into the aorta, dispersed into the head and throughout the hemocoel, then back through the ostia in the heart and the process repeated.
Flatworms, such as this Pseudoceros bifurcus, lack specialized circulatory organs.
Two-chambered heart of a fish
Human anatomical chart of blood vessels, with heart, lungs, liver and kidneys included. Other organs are numbered and arranged around it. Before cutting out the figures on this page, Vesalius suggests that readers glue the page onto parchment and gives instructions on how to assemble the pieces and paste the multilayered figure onto a base "muscle man" illustration. "Epitome", fol.14a. HMD Collection, WZ 240 V575dhZ 1543.
Image of veins from William Harvey's Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, 1628

The blood circulatory system, is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate.

Schematic diagram of the human eye showing the cornea as separated from the sclera by the corneal limbus

Cornea

Transparent front part of the eye that covers the iris, pupil, and anterior chamber.

Transparent front part of the eye that covers the iris, pupil, and anterior chamber.

Schematic diagram of the human eye showing the cornea as separated from the sclera by the corneal limbus
Vertical section of human cornea from near the margin. (Waldeyer.) Magnified. 1: Epithelium. 2: Anterior elastic lamina. 3: substantia propria. 4: Posterior elastic lamina (Descemet's membrane). 5: Endothelium of the anterior chamber. a: Oblique fibers in the anterior layer of the substantia propria. b: Lamellæ the fibers of which are cut across, producing a dotted appearance. c: Corneal corpuscles appearing fusiform in section. d: Lamellæ the fibers of which are cut longitudinally. e: Transition to the sclera, with more distinct fibrillation, and surmounted by a thicker epithelium. f: Small blood vessels cut across near the margin of the cornea.
Corneal cross-section imaged by an SD-OCT
The cornea becomes opaque after death(provenance: genus Bos)
Slit lamp image of the cornea, iris and lens (showing mild cataract)

Because transparency is of prime importance, the healthy cornea does not have or need blood vessels within it.

Types of blood vessels, including a venule, vein, and capillaries

Venule

Types of blood vessels, including a venule, vein, and capillaries

A venule is a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to drain into the larger blood vessels, the veins.

Venous (darker) and arterial (brighter) blood

Blood

Body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.

Body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells.

Venous (darker) and arterial (brighter) blood
Hemoglobin, a globular protein green = haem (or heme) groups red & blue = protein subunits
A scanning electron microscope (SEM) image of a normal red blood cell (left), a platelet (middle), and a white blood cell (right)
Vertebrate red blood cell types, measurements in micrometers
Frog red blood cells magnified 1000 times
Turtle red blood cells magnified 1000 times
Chicken red blood cells magnified 1000 times
Human red blood cells magnified 1000 times
Circulation of blood through the human heart
Basic hemoglobin saturation curve. It is moved to the right in higher acidity (more dissolved carbon dioxide) and to the left in lower acidity (less dissolved carbon dioxide)
Capillary blood from a bleeding finger
Venous blood collected during blood donation
Jan Janský is credited with the first classification of blood into four types (A, B, AB, and O)
Human blood fractioned by centrifugation: Plasma (upper, yellow layer), buffy coat (middle, thin white layer) and erythrocyte layer (bottom, red layer) can be seen.
Blood circulation: Red = oxygenated, blue = deoxygenated
Illustration depicting formed elements of blood
Two tubes of EDTA-anticoagulated blood.

Blood is circulated around the body through blood vessels by the pumping action of the heart.

Diagram of an artery

Artery

Diagram of an artery
Microscopic anatomy of an artery.
Cross-section of a human artery
Arteries form part of the human circulatory system
Diagram showing the effects of atherosclerosis on an artery.

An artery (plural arteries) is a blood vessel in humans and most other animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.).

Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow. (Pulmonary artery labeled at upper right.)

Pulmonary artery

Artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs.

Artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs.

Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow. (Pulmonary artery labeled at upper right.)
Volume rendering of a high resolution CT scan of the thorax. The anterior thoracic wall, the airways and the pulmonary vessels anterior to the root of the lung have been digitally removed to visualize the different levels of the pulmonary circulation.
At the far end, pulmonary arteries (labelled at the bottom) become capillaries at the pulmonary alveoli.
Image showing main pulmonary artery coursing ventrally to the aortic root and trachea, and the right pulmonary artery passes dorsally to the ascending aorta, while the left pulmonary artery passes ventrally to the descending aorta.
Pulmonary circuit
Transverse section of thorax, showing relations of pulmonary artery.
Pulmonary artery
Pulmonary artery.Deep dissection.Anterior view.
CT scan of a normal lung, with different levels of pulmonary arteries.
Bronchial anatomy

The pulmonary arteries are blood vessels that carry systemic venous blood returning to the right side of the heart through to the microcirculation of the lungs.

Nerves (yellow) in the arm

Nerve

Enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.

Enclosed, cable-like bundle of nerve fibers in the peripheral nervous system.

Nerves (yellow) in the arm
Cross-section of a nerve
Micrograph demonstrating perineural invasion of prostate cancer. H&E stain.

Nerves are bundled and often travel along with blood vessels, since the neurons of a nerve have fairly high energy requirements.

Many of the internal organs of the human body

Organ (biology)

Organ is a collection of tissues joined in a structural unit to serve a common function.

Organ is a collection of tissues joined in a structural unit to serve a common function.

Many of the internal organs of the human body
The liver and gallbladder of a sheep
Relationship of major animal lineages with indication of how long ago these animals shared a common ancestor. On the left, important organs are shown, which allows us to determine how long ago these may have evolved.
The flower is the angiosperm's reproductive organ. This Hibiscus flower is hermaphroditic, and it contains stamen and pistils.
Strobilus of Equisetum telmateia
Human viscera

For example, the gland's tissue that makes the hormones is the parenchyma, whereas the stroma includes the nerves that innervate the parenchyma, the blood vessels that oxygenate and nourish it and carry away its metabolic wastes, and the connective tissues that provide a suitable place for it to be situated and anchored.

Transmission electron microscope image of a cross-section of a capillary occupied by a red blood cell.

Capillary

Transmission electron microscope image of a cross-section of a capillary occupied by a red blood cell.
Diagram of a capillary
Depiction of the three types of capillaries. The fenestrated type in the center shows small pores called fenestrations; the sinusoidal type on the right shows intercellular gaps and an incomplete basement membrane and is also known as a discontinuous capillary.
Scanning electron micrograph of a liver sinusoid with fenestrated endothelial cells. Fenestrae are approximately 100 nm in diameter.
This is an annotated diagram of the exchange between capillary and body tissue through the exchange of materials between cells and fluid
Simplified image showing blood-flow through the body, passing through capillary networks in its path.
Depiction of the filtration and reabsorption present in capillaries.

A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter.