Physio quiz 3 & exam

The lymphatic system originates in a

network of terminal sacs or spaces that converge to enter collecting channels.

The interstitial and the lymphatic system together form an

extravascular flow system that plays a crucial role in facilitating exchanges between blood capillaries and tissues.

A primary function of the lymphatic system

to prevent an accumulation of large molecules in the interstitium.

The steady state of the interstitum depends on

on the passage of materials into the lymph system and then back to the bloodstream.

The blood capillary filtrate leaves the

interstitium either by reabsorption or via the lymphatic system.

The lymphatic system is the only route

for the reuptake of filtered plasma proteins.

The intralymphatic pressure is higher

than intravenous pressure in a given tissue.

The main determinants of lymph flow are

filling pressure (preload) and outflow resistance (afterload)

Gravity has no effect on lymphatics due to

discontinuous fluid column

Lymph capillaries starts from tissues spaces as

enlarged blind ended terminals called capillary bulbs

United lymph capillaries form

large lymphatic vessels

Lymph capillaries

* more porous than that of blood capillaries
* have overlapping endothelial cells

The right lymphatic duct opens into

right subclavian vein

The left lymphatic duct (thoracic duct) opens into

left subclavian vein

Lymph vessels are found in all the regions of the body except

* Superficial layers of the skin
* CNS
* Cornea
* Bones
* Alveoli of lungs

Lymph

* clear, colorless


* contains less protein than blood plasma


* high amounts of lymphocytes


* contains few RBC’s


* carries glucose, salts, fat


* dissipates heat


* carrier of fibrinogen

lymph moves through vessels by

* passive
* smooth muscle activity
* stretching of the vessels by the lymph causes rhythmic contractions
* breathing
* heart beat
* tissue massage

Lymphatic pulse pressures are generated by

contraction of the lymphatic vessel smooth muscles

The lymphatic system is not a continuous vessel like the vein as it is

demarcated by lymph valves which supports series of  segments or chamber contractions

Increased stretch caused by an increase in both pre and after load causes a

more powerful rate and strength of contraction which propels lymph

Fluid enters the lymph system through open-ended vessels called

lacteals

The lymph is moved through the body in its own vessels making a one-way journey from

the interstitial spaces to the subclavian veins at the base of the neck.

Lymph is formed from

interstitial fluid

At the venous end of the capillaries

* 1/10th of the blood and the interstial fluid move into lymph vessels
* 9/10th move into venous end of arterial capillaries.

Concentration of lymph takes place in the lymph nodes by

water absorption

How cells enter into the lymph node

* Lymphocytes enter through HEV
* bind to the receptors and are carried into the paracortex
* then migrate into the outer cortex and join specialized dendritic cells and macrophages to form follicles.
* then they migrate to the medulla, where they proliferate as antibody-secreting plasma cells.

HEVs

contain a single layer of large endothelial cells that possess surface receptors specific for B and T lymphocytes.

Primary follicles consist of

a resting B cell surrounded by a loose network of dendritic cells.

After encountering a foreign antigen, the B cell becomes

activated and forms a germinal centre.

The germinal centre and mantle together compose a

secondary follicle, which is the site of antigen-dependent B-cell maturation.

Spleen

* Largest lymphatic organ
* Rich blood supply
* It filters blood
* Large amounts of lymphocytes
* It removes iron from erythrocyte hemoglobin during RBC catabolism
* forms RBC during early fetal life

White pulp

thick accumulation of lymphocytes surrounding an artery

The thymic parenchyma

contains developing T-cells in an extensive meshwork formed by epithelioreticular cells

Thymus cortex

contains epithelioreticular cell types I, II, and III

Thymus medulla

contains epithelioreticular cell types IV, V and VI

The blood-thymus barrier protects

developing lymphocytes in the thymus from exposure to antigens

Peyer’s patches

* located in the ileum
* discrete concentrations of lymphocytes contained in a meshwork of reticular cells

Vermiform appendix

* arises from the cecum
* discrete concentrations of lymphocytes contained in a meshwork of reticular cells

in biological systems pH is calculated using

HCO3 and CO2

An increase in hydrogen ion concentration means

a decrease in pH and the condition is said to be acidic

A decrease in hydrogen ion concentration means

an increase in pH and the condition is said to be basic

The normal pH of mammalian arterial blood is

\~7.4

Tissue cells are relatively tolerant to changes in

hydrogen ion concentrations

Respiratory changes are defined by

changes of arterial PCO2

Metabolic changes are defines as

changes of arterial bicarbonate ion that are not attributable to a change in PCO2

a compensatory mechanism

* will not take the pH from an acidic state all the way to an alkalosis
* vice versa

Respiratory compensation for metabolic disorders is

rapid

Renal metabolic compensation for either respiratory or non-renal metabolic disorders is

 slow

Acids

substances that donate hydrogen ions or protons to a solution

Bases

substances that accept and bind hydrogen ions or protons from a solution

acidemia

A depression of blood pH to below the normal range

alkalemia

blood pH above the normal range

acidosis

The disturbance caused by the addition of  excess acid or removal of base from the ECF

alkalosis

The disturbance caused by the addition of excess base or removal of acid from the ECF

Ingestion in foods and acids/bases

* protein diets give more acid
* diet of plant materials produce basic products

Carbonic acids

* the most important metabolic product of most organic compounds
* dissociates into hydrogen ion (acid) and bicarbonate (base).
* acid accumulation is not a major contributor to the acid pool of the ECF (volatile)

Sulfuric acid

* Non-volatile acids
* from metabolism of sulphur-containing amino acids such as cysteine and methionine

Phosphoric acid

* Non-volatile acids
* formed from hydrolysis of the phosphodiester of phosphoproteins and phospholipids

Ammonium compounds

* ammonia combines with carbonic acid to form ammonium and bicarbonate.
* ammonium goes to the liver and combines with carbon dioxide to form hydrogen, urea and water
* hydrogen recombines with bicarbonate to reform carbonic acid

Acid-base buffer system

* participates to prevent pH changes when either a strong acid or a strong base is present
* When a strong acid is added, it reacts with the weak base
* When a strong base is added, it reacts with the weak acid

Bicarbonate buffer system

* Principal buffer system
* The weak base component in the buffer is HCO3-
* Bicarbonate buffer system prevents the fall of pH in a fluid to which strong acid has been added.
* all the components of the system are separately regulated by the renal and respiratory systems respectively

Phosphate buffer system

* This system is useful in the ICF as the concentration of phosphate is more in ICF than ECF.
* This system is comprised of sodium dihydrogen phosphate (weak acid) and disodium hydrogen phosphate (weak base)

Protein buffer system

* Found in plasma and red blood cells
* Weak acids (C-terminal carboxyl group, N-terminal amino group)
* protein that form the weak acids is the reduced hemoglobin and proteinate ions of hemoglobin form the weak base.

Hemoglobin buffer system

* Hemoglobin is the second most important blood buffer and the most important and effective protein buffer.
* six times more buffering capacity than the plasma proteins.

Acidosis causes

* potassium ion to move from cells to extracellular fluid in exchange for hydrogen ions, and alkalosis causes the reverse movement of potassium and hydrogen ions.
* depression of synaptic transmission in CNS

Alkalosis

over excitability of CNS and peripheral nerves

Distribution system

Heart, aorta and it’s branches, smaller arteries, and arterioles

Distribution/perfusion

arterioles and capillaries

The collecting system

venules, large veins, vena cava and heart

The arterial system

* is the resistance component
* distributes
* output
* Resistance is directly proportional to pressure and inversely proportional to flow
* major resistance sites occur at the precapillary beds

The venous system

* input
* is the capacitance component
* collects and returns blood to the heart.
* Capacitance is directly proportional to volume and inversely proportional pressure

portal systems

occur in the renal, digestive and hypothalamic systems.

Preload

* means incoming blood to the heart.
* It is determined by the expansibility of the low pressure venous system vessels.
* is the end-diastolic volume (EDV) at the beginning of systole. The EDV is directly related to the degree of stretch of the myocardial sarcomeres.

Afterload

* means the resistance that the heart encounters to propel blood out of the heart through the ventricles.
* It is determined by the high pressure of the arterial system
*  simply means  the ventricular pressure at the **end** of systole (ESP) or increased ventricular pressure to eject blood

Gravity

has great effect on the vascular pressure at the level of the heart as determined by hydrostatic pressure.

The lungs are

a low pressure system

The heart has free communication between

the atrium and the ventricles of each side

Three types of muscles are found in the heart.

* Atrial muscles
* Ventricular muscle
* Specialized excitatory and conductive muscle fibers.
* Syncytium of fibers

Properties of heart muscle

* Spontaneous rhythmicity.
* Action potential is greatly prolonged
* Contractile force is directly proportional to the degree of stretching.

Conducting pathway of cardiac AP

* Impulses generated in the S.A. node
* Atrioventricular bundle (A V- bundle).
* Right and left bundles of His.  
* Purkinje system

Action Potential Of A Cardiac Muscle

* In cardiac muscle the excited membrane does not repolarize immediately after depolarization
* The potential remains on a plateau near the peak of the spike sometimes for many milliseconds before repolarization begins.

Phase 0

is caused by the rapid and relatively large influx of sodium ions (fast inward current) into the cell.

Phase 1

the early phase of repolarization, is caused by the transient outward movement of potassium ions

Phase 2

the plateau phase, is attributed to the continued, but decreased, entry of sodium and a large, but slow, influx of calcium ions into myocardial cells.

Phase 3

is the phase of repolarization during which the membrane potential returns to its resting value because of potassium efflux from the cell

Phase 4

is a resting phase in atrial and ventricular muscle cells prior to the initiation of the next action potential.

Significance of the Plateau

Protects the heart from too many frequent and out of phase contraction.

Lead 1

* Left forelimb electrode connected to the positive terminal
* Right forelimb electrode connected to the negative terminal

Lead II

* Left hind limb electrode connected to the positive terminal
* Right forelimb electrode connected to the negative terminal of the voltmeter.

Lead III

* Left hind limb electrode is connected to the positive terminal.
* Left forelimb electrode is connected to the negative terminal.

negative

when any two points are connected to one electrode or terminal of the voltmeter

positive

remaining electrode on one limb is connected to the remaining terminal of the voltmeter

Augmented limb lead, are designated as follows

* AvR right forelimb
* AvL left forelimb
* AvF left hind limb

avR

Here the voltage from the right forelimb (positive) is compared with the average voltage from the other two limbs connected together and then to the negative

avL

Here the voltage from the left forelimb (connected to positive terminal) is compared with the average voltage from right forelimb and left hind limb which are connected together and then to the negative terminal of the voltmeter.

avF

 Here the voltage from the left hind limb (connected to positive terminal) is compared with the average voltage from right and left fore limbs which are connected together and then to the negative terminal of the voltmeter.

P 

Immediate depolarization of the atrial muscles

QRS

Generalized depolarization of the entire conducting system and ventricular musculature. 

T

This represents the period of recovery of the ventricle from contraction or depolarization. It is therefore, the wave of ventricular repolarization.

U 

Vibration of papillary muscles