**A&P 2 Unit 17 & 18 (Lab) [Blood Vessels] Flashcards
The Blood Flow of the Brain
The arterial supply of the brain comes primarily from the internal carotid arteries & the basilar artery.
Basilar Artery
Located on the base of the brainstem & is derived from the fusion of 2 branches off of the subclavian arteries called the vertebral arteries.
Cerebral Arterial Circle
Once the internal carotid arteries & basilar artery enter the brain, they contribute to a structure called the circle of Willis or Cerebral Arterial Circle
Cerebral Arterial Circle (Composition)
- This circle is composed of branches of these vessels & a set of anterior & posterior communicating arteries.
- These vessels are connected to provide alternate routes of circulation to the brain if one of the arteries supplying the brain becomes blocked.
Veins that Drain into the Hepatic Portal Vein
- Splenic Vein
- Gastric Veins
- Superior Mesenteric Vein
- Inferior Mesenteric Vein
DO NOT drain directly into the Inferior Vena Cava.
Splenic Vein
Drains the Spleen
Gastric Veins
Darin the Stomach
Superior Mesentric Vein
Drains the Small Intestine & much of the Large Intestine
Inferior Mesentric Vein
Drains the remainder of the Large Intestine
Renal Veins
- Drain the Kidneys
- Empties into the Inferior Vena Cava
Hepatic Portal Vein
- Here, the nutrient-rich blood percolates through the liver, where it is processed & detoxified.
- In this way, everything we ingest (except lipids) must travel through the liver before entering the systemic circulation.
- Once the blodd has filtered through the hepatic portal system, it exits via Hepatic Veins & drains into the Inferior Vena Cava
- Blood glucose (absorbed during digestion) is converted to glycogen for storage in the liver. We’ll breakdown that glycogen between meals. Environmental toxins (e.g. pesticides, drugs) can be broken down by liver cells as a means of detoxification. Pathogens (e.g. bacteria) are phagocytosed by macrophages in the liver. The blood, now “cleaner” and “detoxed” leaves the liver through the hepatic veins which drain into the inferior vena cava.
Three Layers of the Walls of Arteries & Veins
- Tunica Interna
- Tunica Media
- Tunica Externa
Tunica Interna
- The innermost lining of the blood vessel.
- It consists of a specialized type of simple squamous epithelium called endothelium.
- It rests on top of a thin layer of connective tissue.
Tunica Media
- The middle layer of the blood vessel wall & consists of smooth muscle & elastic fibers.
- The smooth muscle, innervated by the sympathetic nervous system, controls the diameter of the vessel & plays an important role in tissue perfusion & blood pressure.
- The elastic fibers allow the vessel to expand with changing pressure & return to its original shape & diameter.
Tunica Externa
- Also known as Tunica Adventitia
- The outermost layer of the blood vessel, which consists of dense irregular collagenous connective tissue with abundant collagen fibers. The collagen fibers reinforce the blood vessel & prevent it from rupturing when the pressure in the vessel increases.
Artery (Mean Diameter)
4.0 mm
Artery (Mean Wall Thickness)
1.0 mm
Arteriole (Mean Diameter)
30.0 µm
Arteriole (Mean Wall Thickness)
6.0 µm
Capillary (Mean Diameter)
8.0 µm
Capillary (Mean Wall Thickness)
0.5 µm
Venule (Mean Diameter)
20.0 µm
Venule (Mean Wall Thickness)
1.0 µm
Vein (Mean Diameter)
5.0 mm
Vein (Mean Wall Thickness)
0.5 mm
Arteries (Composition) [Most to Least]
- Smooth Muscle
- Elastic Tissue
- Fibrous Tissue
- Endothelium
Capillaries (Composition) [Most to Least]
- Endothelium
Veins (Composition) [Most to Least]
- Smooth Muscle
- Elastic Tissue & Fibrous Tissue
- Endothelium
Three Types of Capillaries
- Continuous Capillary
- Fenestrated Capillary
- Sinusoid
Continuous Capillary
Are continuous in the sense that the endothelial cells provide an uninterrupted lining, and they only allow smaller molecules, such as water and ions to diffuse through tight junctions, leaving gaps of unjoined membrane called intercellular clefts.
Continuous Capillary (Location)
Most common, found in most locations in the body.
Fenestrated Capillary
- Have pores in the endothelial cells (60-80 nm in diameter) that are spanned by a diaphragm of radially oriented fibrils and allow small molecules and limited amounts of protein to diffuse.
- In the renal glomerulus there are cells with no diaphragms called podocyte foot processes or “pedicels,” which have slit pores with an analogous function to the diaphragm of the capillaries.
- Both of these types of blood vessels have continuous basal lamina.
Fenestrated Capillary (Location)
- Endocrine Glands
- Intestines
- Pancreas
- Glomeruli of Kidney.
- Less common, fenestrated capillaries are found, for example, in the kidneys for the filtration of blood during urine production.
Sinusoid Capillary
- A special type of fenestrated capillaries that have larger openings (30-40 μm in diameter) in the endothelium.
- These types of blood vessels allow redand white blood cells (7.5μm - 25μm diameter) and various serum proteins to pass aided by a discontinuous basal lamina.
- These capillaries lack pinocytotic vesicles, and therefore utilize gaps present in cell junctions to permit transfer between endothelial cells, and hence across the membrane.
- Some sinusoids are special, in that they do not have the tight junctions between cells.
- They are called discontinuous sinusoidal capillaries, and are present in the liver and spleen where greater movement of cells and materials is necessary.
- Their extremely porous walls allow new formed elements to easily enter the circulation from their “birthplace” in the red marrow.
Sinusoid Capillary (Location)
- Bone Marrow
- Lymph Nodes
- Adrenal Gland
Pulse
A rhythmical throbbing of the arteries as blood is propelled through them
Pulse Palpation
- The process of feeling the pulse with the fingertips.
- It is performed to assess rate, rhythm, & regularity of the heartbeat & to assess the arterial circulation to different parts of the body
Pulse Palpation Measuring Locations
- Radial
- Ulnar
- Brachial
- Carotid
- Temporal
- Femoral
- Popliteal
- Posterior Tibial
- Doralis Pedis
Carotid Bruit
- It may occur as the result of carotid artery stenosis (though some disagree); however, most carotid bruits, particularly those found in younger or asymptomatic patients, are not related to any disease and are termed “innocent carotid bruits”.
- A carotid bruit is unlikely to be heard if the stenosis occludes less than 40% of the diameter of the artery.
- Likewise, a stenosis of greater than 90% may not be heard, as the flow may be too low.
Capillary Refill Time
The time it takes for capillary beds to refill after they have been forcibly emptied by pressure.
Capillary Refill Time (Examination)
- Done to evaluate a patient for a variety of vascular diseases, particulary arterial disease.
- A normal capillary refill time measures 1-3 seconds; a value greater than 3 seconds may signify some sort of pathology.
- Finger nail test
Blood Pressure
The pressure exerted by the blood on the walls of the blood vessels.
Cardiac Output
- The amount of blood each ventricle pumps in 1 minute.
- It is a product og stroke volume, or the amount pumped with each beat, & heart rate.
Peripheral Resistance
- Any impedance to blood flow encountered in the blood vessels.
- It is determined largely by the degree of vasoconstriction (increase) or vasodilation (decreases) in the systemic circulation.
- Other factors that influence resistance include obstructions, such as atheromatous plaques, within arteries.
Blood Volume
- The amount of blood found in the blood vessels at any given time is known as the bloof volume.
- It is greatly influenced by overall fluid volume & is largely controlled by the kidmeys & hormones of the endocrine system.
Systolic Pressure
- The pressure in the arteries during ventricular systole.
- This is the larger of the two readings, averaging between 100 & 120 mmHg.
- Taken when the first sounds are heard
Diastolic Pressure
- The pressure in the arteries during ventricular diastole.
- This is the smaller of the two readings, averaging between 60 & 80 mmHg.
- Taken when the sounds disappear.
Vertebral Artery
Common Carotid Artery
Subclavian Artery
Brachiocephalic Trunk
Axillary Artery
Ascending Aorta
Brachial Artery
Radial Artery
Ulnar Artery
Digital Arteries
Palmer Arches
Popliteal Artery
Fibular Artery
Dorsalis Pedis Artery
Plantar Arch
Aortic Arch
Descending Aorta
Celiac Trunk
Renal Artery
Gonadal Artery
Lumbar Artery
Common Iliac Artery
Internal Iliac Artery
External Iliac Artery
Deep Femoral Artery
Femoral Artery
Posterior Tibial Artery
Anterior Tibial Artery
