Week 3 Concepts

Anatomy and functional roles of different types of blood vessels:

·        Most blood vessels (with the exception of capillary beds) contain three layers

o   Tunica externa – epithelial cells, connective tissue, elastic fibers

o   Tunica media – elastic fibers and smooth muscle (usually the largest layer)

o   Tunica intima (interna) – endothelial cells, connective tissue

·        Arteries

o   Elastic arteries – largest arteries by diameter; contain more elastic fibers than smooth muscle, thick tunica media

o   Examples of elastic arteries include pulmonary, aorta, brachiocephalic, common carotid, subclavian, and common iliac arteries.

o   Muscular arteries – Contain large amounts of smooth muscle (also known as distributing arteries); most named arteries in the body fall into this category

o   Examples of muscular arteries: brachial artery, femoral artery, radial artery, splenic artery, and mesenteric artery.

o   Arterioles (resistance, slows down blood) – smallest arteries by diameter; slightly larger than the diameter of one red blood cell; attached to the capillary beds; pre-capillary sphincter (chemoreceptor for oxygen) used to control blood flow through the systemic capillary

·        Capillaries – diameter roughly the size of one red blood cell; site of the exchange of fluids and nutrients/waste; only have tunica intima

o   Continuous – overlapping endothelial cells; filtration cleft; only small molecules can fit through; diffusion and bulk flow endocytosis; found in systemic capillaries

o   Fenestrated – contains pores in addition to filtration cleft; allows for slightly larger molecules to filter; found in places like the kidney

o   Sinusoidal (think of Swiss cheese, large holes) – larger filtration pores; large molecules can filter; found in the liver

o   Capillary filtration and reabsorption (what proteins are involved, how much fluid leaks out and how much is reabsorbed, etc.)

·        Veins: hold most of body’s blood at any given time; contain valves; rely on the following to create pressure to assist in returning blood to the heart: vasoconstriction, valves, skeletal muscle pump, respiratory pump, and cardiac suction.

o   Venules – smallest veins in diameter; attached to capillary bed

o   Medium sized veins – slightly larger diameter veins

o   Large veins – largest diameter veins; roughly the size of a garden hose; inferior vena cava is best example

o   Hepatic portal system: drains blood from GI tract, pancreas, GB, spleen. 2 capillary beds: 1 – intestines + digestive organs, 2- hepatic sinusoids in liver. Intestinal blood richly laden with nutrients goes to liver before the rest of the body, allows liver to filter pathogens.

·        Flow of blood through the pulmonary and systemic circulation and when it is and isn’t oxygenated

Systemic Circulation

·        Be able to identify each of the following blood vessels on an image (pretty detailed)

·        Be able to determine blood flow (example: blood in the axillary artery will go where next or blood in the cephalic vein will go where next?)

o   Major arteries and veins

Hepatic portal vein- drains blood from the intestines to the liver.

Hepatic vein- takes blood from the liver to the inferior vena cava.

Large vein example: inferior vena cava.

Protein always stays in the blood albumin.

The abdominal aorta splits into the right and left common iliac. The right and left common iliac become the right and left internal and external iliac. The internal iliac goes into the pelvic bowl. The external iliac arteries continue into the legs.

Coronary arteries feed the heart with blood, oxygen, and nutrients.

Common carotid arteries take blood to the skull, brain, and neck region.

The subclavian arteries go into the upper extremities.

Aortic arch consists of:

·        Brachiocephalic trunk

·        Left common carotid

·        Left subclavian

3 unpaired branches of the abdominal aorta:

·        Celiac trunk

·         superior mesenteric

·        inferior mesenteric

5 paired branches of the abdominal aorta:

·        R&L inferior phrenic

·        R&L supra renal

·        R&L renal arteries

·        R&L lumbar arteries

·        R&L gonadal arteries

 At the metarteriole-capillary junction, the distal-most muscle cells form Precapillary sphincters, which monitor the blood flow into the capillary.

The most important method of capillary exchange is diffusion.

Cardiac Output = HR x SV

Stroke Volume = EDV - ESV

Which pressure promotes reabsorption? Blood colloid osmotic pressure

Blood pressure and the interrelationships with cardiac output, peripheral resistance and hemodynamics

·        Blood flow = the change in pressure (P_aorta – P_{R atrium}) / resistance

·        MAP = (systolic pressure – diastolic pressure)/3 + diastolic pressure

·        Three factors determine systemic vascular resistance.

o   Blood vessel diameter:

o   vasoconstriction:  increase in pressure.

o   vasodilate: decrease in pressure.

§  A decrease in vessel diameter increases resistance and requires an increase in pressure to maintain the original flow rate.

o   Blood vessel length:

o   Longer means greater resistance, whereas shorter means less resistance and more pressure required

§  An increase in blood vessel length increases resistance and requires an increase in blood pressure to maintain the original flow rate

o   Blood viscosity:

o   Thicker blood means greater resistance

§  An increase in viscosity results in thicker blood that is harder to move and requires an increase in blood pressure to maintain the original flow rate

·        Cardiac output is the amount of blood pumped out of the left ventricle per minute so it will directly influence blood pressure in the blood vessels

·        Concept of Frank-Starling law

·        Blood vessel diameter can be changed on a second-to-second basis.

·        BCOP- BLOOD COLLOID OSMOTIC PRESSURE

·        IFOP- INTERSTITIAL FLUID HYDROSTATIC PRESSURE

Application of Homeostatic Mechanisms

·        Should resistance change, pressure must change accordingly to maintain the same rate of blood flow (CO). Blood vessel diameter is the one resistance we can control immediately so it is most commonly used to control blood pressure

·        Equations: CO, SV, MAP

·        Know what would happen to blood pressure with each change in resistance, contractility, sympathetic and parasympathetic input, etc.

·        Capillary Net Filtration Pressure (NFP = (BHP + IFOP) – (BCOP + IFHP))

o   Two factors that promote filtration are BHP and IFOP

o   Two factors that oppose filtration are BCOP and IFHP

o   Net positive number equals filtration (fluid moving from the blood into the interstitial fluid)

o   Net negative number equals reabsorption (fluid moving back into the blood from the interstitial fluid

o   If the amount of fluid that is reabsorbed on the venous end does not equal the amount of fluid filtered on the arterial end, an accumulation of fluid can happen in the interstitial space. This is called EDEMA

·        Veins contain most of the blood at any given time and function as a blood reservoir that can dramatically increase venous return to the heart when systemic venoconstriction increases venous return.

Week 4 Concepts

General functions of Lymphatic System

·        Fluid balance – takes fluid filtered from the blood into the interstitial space and returns it to the bloodstream through lymphatic vessels

·        Formation of lymph – lymph resembles interstitial fluid since it is essentially the same fluid only in the lymph vessel

·        Transports lipids – in the form of lacteals

·        Provides Immunity – due to the housing and transport of many WBCs in lymphatic tissues

Primary lymphatic structures:

·        Thymus

·        Red bone marrow

Secondary lymphatic structures:

·        Everything else is secondary

Lymph and lymphatic vessels

·        Filtered blood plasma, including solutes and occasionally leaked plasma proteins, leaves the blood stream and enters the interstitial fluid. Most of that fluid gets reabsorbed on the venous end of the capillary bed, however some of the fluid is left behind. That fluid is taken up by the lymphatic capillary bed and becomes lymphatic fluid. This fluid is then drained through the lymphatic vessels, then trunks, and lastly ducts that will drain the fluid into the subclavian veins thus returning the fluid back to the blood vessel where it originated.

·        Lymphatic capillaries resemble continuous blood capillaries but have some differences

o   Larger filtration clefts allowing for larger substances to be absorbed

o   Lymphatic capillaries are closed on one side (‘blind-ended’) whereas blood has an arteriolar side and venous side

o   Lymphatic capillaries require tethering to surrounding tissue to prevent collapse and assist opening filtration clefts

·        Lymphatic capillaries absorb interstitial fluidfhe via bulk flow through clefts, facilitated diffusion, and transcytosis

·        Lymph flows as follows: Interstitial fluid to Lymphatic capillaries to afferent lymphatic vessels to lymph nodes to efferent lymphatic vessels to lymphatic trunks to lymphatic ducts to the subclavian veins

·        Lymphatic Ducts

o   Right lymphatic duct – drains right side of the body above the diaphragm

o   Thoracic duct – drains left side of the body above the diaphragm and both lower extremities

o   Cisterna chyli – name of the structure where the two lymphatic trunks from the lower extremities join together.

Lymphatic cells, tissues and organs

·        Lymphatic vessels

·        Lymphatic tissues - groups of lymphocytes within CT, mucous membranes, and various organs

o   MALT – mucosa associated lymphatic tissue; lymphatic tissues that line organs open to the exterior like respiratory, digestive, urinary, and reproductive tracts

§  GALT – Gastrointestinal associated lymphatic tissue (found in the mucosa of most GI structures

§  Peyer’s patches – found in the SI

·        Lymphatic organs – Non-moving structures that work to house lymphatic tissue

o   Red bone marrow

o   Lymph nodes

o   Tonsils

o   Thymus

o   Spleen

·        Structure, function, and major locations of lymphatic tissues

o   Lymph nodes – lymphatic tissue surrounded by a capsule; primary function is to remove unwanted waste; cortex and medulla sections housing B-cells, T-cells, macrophages, and antigen presenting cells.

§  MALT

§  Tonsils – found in pharynx and oral cavity – helps to trap inhaled or ingested foreign substances

·        Pharyngeal tonsils

·        Palatine tonsils

·        Lingual tonsils

o   Thymus: found superior to the mediastinum between the two lungs, deep to the sternum; site of T-cell maturation and growth; shrinks as we age and is replaced with adipose tissue; produces hormones that help to mature the T-cell Lymphocytes

o   Spleen: largest lymphatic tissue in the body; upper right quadrant; surrounded by a capsule

§  Red pulp – blood reservoir; helps to rid the body of old or damaged RBCs

§  White pulp – consists of B-cells, T-cells, and macrophages and functions similar to a large lymph node