PTA Program: Unit 6 - Edema (PTH 121) PDF

TCC PTA Program **[PTH 121 - Unit 6 -- HO \#1 -- Edema] [Reference]: O'Sullivan 7^th^ ed (Ch14)** Upon completion of this unit, including lecture and laboratory attendance, completion of reading assignments and review of handout materials, the student will be able to: A1.      Describe the conn...

TCC PTA Program **[PTH 121 - Unit 6 -- HO \#1 -- Edema] [Reference]: O'Sullivan 7^th^ ed (Ch14)** Upon completion of this unit, including lecture and laboratory attendance, completion of reading assignments and review of handout materials, the student will be able to: A1.      Describe the connection between the arterial, venous, and lymphatic systems. A2.      Compare and contrast the roles of the venous and lymphatic systems in returning blood to the heart. B1.      Describe the fluid compartments in the body. B2.      Describe the modes of fluid transport in the body. B3.     Describe the pathophysiology of edema. **[Anatomy and Physiology of the Vascular and Lymphatic Systems]** **Blood and lymph vessels permeate most tissues, carrying oxygen and nutrients while removing carbon dioxide and waste. Arteries and veins are too large and have thick walls, thus do not allow diffusion between the bloodstream and surrounding tissues. A delicate network of blood and lymph capillaries are woven throughout most tissues in the body controlling all chemical and gaseous exchange between blood, interstitial fluid, and lymph.** **[Vascular System] (Arteries and Veins)** 1. **[Arteries]: carry rich, oxygenated blood away from the heart, branching off into smaller [arterioles], and even smaller [capillaries]. Arteries have three layered walls that give them strength and elasticity that allows them to withstand high pressures generated by the heart. Arteries are strong and durable and maintain their cylindrical shape when stretched. The movement of blood through arteries is dependent on heart function. Arteries can change shape depending on blood flow. They contract (vasodilate) and relax (vasodilate) due to ANS (SNS) innervation.** - **i.e., When a bear is chasing you, you run for your life. Your heart (pump) beats fast pumping out a large volume of blood. Your arteries undergo vasoconstriction (stiff pipes) to meet the demand of the large volume of blood. The SNS (fight or flight) causes an increase in heart rate, vasodilation of coronary arteries (oxygen to the pump), and vasoconstriction of peripheral arteries (stiff pipes).** - **[Arterial wounds] are dry because there is not enough arterial blood getting to tissue.** 2. **[Veins]: return deoxygenated blood from tissues and organs to the heart. Venous blood begins at the small [capillaries], passes into [venules], and into [veins] (superficial, deep, and perforating). Superficial veins run on top of muscular fascia, deep veins run below muscular fascia, and perforating veins connect the superficial and deep veins, perforating the fascia. Veins also have three layered walls, but they are not elastic or muscular because venous pressures are much lower. Venous walls are so thin, they do not hold their shape, they easily collapse, or tear when stretched. Since the pressure in the venous system is low, the veins contain valves projecting from the inner venous wall, pointing in the direction of blood flow. Under normal conditions, valves prevent the backflow of blood as blood is moved toward the heart by any movement that compresses the veins. This is primarily skeletal muscle contraction which occurs from walking, (or in the case of surgery), ankle pumps and compression pumps. When venous walls weaken or become enlarged, valves cannot function properly and blood begin to pool in the veins, primarily in the LEs. Eventually the veins remain distended leading to [varicose veins]. When valves fail to close properly, this leads to [venous reflux].** - **[Venous wounds] are wet because blood is collecting in the veins, venules, and capillaries and seeping into interstitial spaces.** **[Lymphatic System]** **The lymphatic system runs parallel to and works together with the venous system. The lymphatic system is often described together with the immune and integumentary systems because they are closely related.** **[Primary functions of the lymphatics] (2):** 1. **Protect the body from infection and disease via the immune response.** 2. **Facilitate movement back and forth between the bloodstream and the interstitial space, removing excess fluid, blood waste, and protein molecules in the process of fluid exchange.** **Lymphatics are located throughout the body except in the central nervous system (brain and spinal cord) and cornea.** **Lymphatic system includes:** **1-Lymph vessels** **Superficial, intermediate, and deep (commonly referred to as lymphatics)** -------------------------------- ------------------------------------------------------------------------------ **2-Lymph fluid** **3-Lymph tissues and organs** **Lymph nodes, tonsils, spleen, thymus, thoracic duct** Lymph fluid is first absorbed at the [capillary level], then channeled through small vessels called [precollectors], and finally through larger, valved vessels called [collectors]. The collectors have smooth muscle, contractile properties, and valves. Lymphatic vessels are even thinner and more likely to collapse than veins. Lymph moves through the body by several mechanisms. Superficially this occurs via diffusion and filtration. Below the dermis, lymph moves in the larger collector vessels by intrinsic contraction of [lymphangions] (small pump-like segments within the larger collectors). Difference between Blood and Lymph - MD New literature is evolving helping us to better understand the movement of lymph by stimulating lymphangions. The following are stimuli that affect lymphangion contraction, and thus, cause movement of lymph: - Stimulation of sensory nerves, SNS and PSNS nerves - Skeletal muscle contraction adjacent to lymphatic vessels - Pulsation of arteries adjacent to lymphatic vessels - Abdominal and thoracic cavity pressure changes that occur with normal breathing - Volume changes within lymphangions - Mild mechanical stimulation of dermal tissues (this is how Manual Lymphatic Drainage (MLD) works) Lymph fluid is transported back to the heart where it re-enters venous circulation where the pressure is lowest. Fluid from the right side of the head, neck, thorax, and R UE drains into the [R lymphatic duct] which dumps into the venous circulation at the junction of the right internal jugular and right subclavian veins. Fluid from the rest of the body drains into the [thoracic duct] on the left side of the body which dumps into the venous circulation at the junction of the left internal jugular and left subclavian veins. Under normal conditions, lymph flow is not adversely affected by gravity. Under abnormal conditions, lymph pools especially in the LEs. Lymphatic System Notes[Lymphatic system](https://image.slidesharecdn.com/lymphaticsystemnotes-120330134955-phpapp01/85/lymphatic-system-notes-7-638.jpg?cb=1665816180) **[Overview of Fluid Compartments in the Body]**: [Reference]: Goodman (Ch 5) About 45-60% (45-50% in aging adult vs. 55-60% in younger adults) of the adult body is composed of water which contains electrolytes. This life sustaining fluid is found in four compartments: - - [Intracellular space] (within cells) - [Interstitial space] (between cells) - [Intravascular space] (within blood vessels) - [Transcellular space] (separated from body tissues by epithelial cells -- includes digestive juices, CSF, synovial fluid, intraocular fluid, and water/solutes in the renal system and bladder). Makes up a very small amount of body's fluid. [Two kinds of fluid]: 1. [Extracellular fluid (ECF)]: fluid located in the **intravascular** and **interstitial spaces** (about 1/3 of body's fluid) 2. [Intracellular fluid (ICF):] fluid located in the **intracellular spaces** (about 2/3 of body's fluid) Maintaining homeostasis requires the proper balance between ICF and ECF to provide nutrition to the cells and allow for removal of waste products. A fluid imbalance occurs when the ICF or ECF either gains or loses fluids or electrolytes. Sodium is the ion that most influences water loss and water retention.  Image result for fluid volume deficit mnemonic **[Fluid volume excess]** occurs when there is an overabundance of water in the interstitial space or body cavities (**[edema]**) or in the blood vessels (**hypervolemia**). Characterized mostly by weight gain and edema of the extremities. Excess fluid in the intravascular space results in dyspnea, engorged neck veins, and a bounding pulse. **[Fluid volume deficit]** occurs when there is an excessive loss of water or an inadequate intake of water. The clinical manifestation is **[dehydration]** which can lead to vascular collapse (**hypovolemia**) and shock if left untreated. Dehydration occurs due to hemorrhage, GI bleed, burns, diarrhea, vomiting, diaphoresis, or lack of fluid intake. **[Fluid shift]** occurs when fluid that belongs in one space shifts to a different space and remains there. This is referred to as [third-space fluid] and is the result of trauma, inflammation or most commonly, liver disease. Other potential spaces that can fill with fluid are the peritoneal cavity (**[ascites]**) and the pleural cavity (**[pleural effusion]**). **[Fluid Transport within the body]:** **1. Structures/substances** involved with fluid transport within the body: 1\. [Solute] -- the particles that are dissolved in a liquid (ex. Kool-Aid powder) 2\. [Solvent] -- the liquid that dissolves the particles (solute) (ex. Water) 3\. [Solution] -- solute dissolved in solvent (ex. Kool-Aid powder and water) 4\. [Plasma Membrane] -- tissue that separates the inside of the cell and the outside of the cell. -has an electrochemical gradient -the inside of cells are more negatively charged than the outside -certain particles can passively move through the membrane while others must be actively transported. **Modes of fluid transport** within the body (3): ------------------------------------------------- 1. [Diffusion] -- movement of particles (solute) from an area of high particle (solute) concentration to an area of low particle (solute) concentration until equilibrium is achieved 2. [Osmosis] -- movement of fluid (solvent -- usually water) from a region of low particle (solute) concentration to an area of higher particle (solute) concentration until equilibrium is reached 3. [Active Transport] -- mode of transport for particles that are too large (plasma proteins), have the wrong charge or must move against their concentration gradient, to cross the plasma membrane 3\. Fluid Transport: how it works: 2\. Large molecules are retained in the blood, although some leakage does occur. 3\. Water and solutes pass into the interstitial space. **[Pathophysiology of Edema]**: +-----------------------------------+-----------------------------------+ | Normal Situation | Pathologic Situation | +-----------------------------------+-----------------------------------+ | Higher pressure exists at the | High pressure exists at the | | arterial end of capillaries, | arterial end of capillaries, thus | | allowing fluids to move into the | allowing movement of fluids into | | interstitial space. | the interstitial space. | | | | | Some fluid passes back into the | The venous system becomes | | venous end of capillaries, which | [blocked], causing ↑ | | have lower pressure. | pressure at the venous end of the | | | capillaries. | | The remaining fluid passes into | | | the lymphatic vessels as lymph. | Fluid cannot move into an area of | | | lower pressure, so fluid remains | | | in the interstitial space | | | resulting in edema. | | | | | | If fluid cannot be removed via | | | the venous system, the body | | | employs the lymphatic system on a | | | more full-time basis. | | | | | | The lymphatic system may or may | | | not be able to handle the ↑ | | | volume of lymph required to | | | return to the venous circulation. | +-----------------------------------+-----------------------------------+