Urinalysis & Body Fluids Lecture Notes PDF

Urinalysis & Body Fluids MLT 004- 2 Credits Lecturer: Ms. Yeama Singh Anatomy & Physiology Lecture 1 Overview of the Urinary System ► Urinary system consists of: ❑ Two kidneys ❑ Two Ureters ❑ Single Urinary Bladder ❑ Single Urethra ❑ Note: Urine is stored i...

Urinalysis & Body Fluids MLT 004- 2 Credits Lecturer: Ms. Yeama Singh Anatomy & Physiology Lecture 1 Overview of the Urinary System ► Urinary system consists of: ❑ Two kidneys ❑ Two Ureters ❑ Single Urinary Bladder ❑ Single Urethra ❑ Note: Urine is stored in the bladder and excreted by the process of Mictrution Major Organs of the Urinary System Ureter ► The ureter carries urine from the kidney to the urinary bladder. ► It is approximately 25-30 cm long, with a diameter of approximately 3 mm. ► It is continuous with a funnel shaped renal pelvis ► As urine accumulates and the pressure in the bladder rises, the ureters are compressed , this prevents the black-flow of urine into the ureters. Ureter The walls of the ureters consists of 3 layers of tissue: 1. An outer covering of fibrous tissue 2. A middle Muscular layer consisting of interlacing smooth muscle fibers. 3. An inner layer , the Mucosa, composed of transitional epithelium. Function of Ureter Peristaltic waves occur several times per minute, increasing in frequency with the volume of urine produced, sending little spurts of urine along the ureter towards the bladder Urinary Bladder ► The Urinary Bladder is a reservoir for urine, it lies in the pelvic cavity and the size and position can vary, depending on the volume of urine it contains. The bladder is composed of three layers: 1. The outer layer of loose connective tissue, containing blood and lymphatic vessels and nerves. 2. The middle layer, consists of interlacing smooth muscle fibers and elastic tissue loosely arranged in three layers. This is called the Detrusor Muscle and when it contracts, it empties the bladder. 3. The inner mucosa, is composed of transitional epithelium that readily permits distention of the bladder as it fills. Urinary Bladder ► When the bladder is empty, the inner lining is arranged in folds, or rugage, which gradually disappear as it fills. ► The total capacity is not usually more than 600mls. The three orifices in the bladder form a triangle or Trigone. 1. The upper two orifices on the posterior wall are the opening to the ureters 2. The lower orifice is the opening into the urethra. 3. The internal urethral sphincter, a thickening of the urethral smooth muscle layer in the upper part of the urethra, controls outflow of urine from the bladder. This sphincter is not under voluntary control. Urinary Bladder Urethra ► The urethra is the canal that extends from the neck of the bladder to the exterior, at the external urethral orifice. It is longer in the males than females. ► The male urethra is approximately 20cm Long, and is associated with both the urinary and reproductive systems. ► The female urethra is approximately 4cm Long, and 6mm in Diameter. The wall of the Urethra has 2 layers: 1. An outer Muscle Layer 2. An inner Lining of Mucosa The external urethral sphincter is under voluntary control. Urethra Overview of the Urinary System Urinary System: ► Filters dissolved material from the blood. ► Regulates electrolytes & Fluid Volume ► Concentrates and Release Waste Products ► Reabsorbs substances (Water, Nutrients, Minerals) within the circulatory system through a process called tubular reabsorption. ► Secretes Urea: drugs, ions, hormones & enzymes. ► Excrete metabolic wastes (Urine) Urine Formation Urine Formation is the result of three processes: ► Filtration ► Reabsorption ► Secretion ► These processes occur within tiny structures called nephrons. The amount of urine produced by nephrons is controlled by hormones ADH and Aldosterone Urine Formation Urine formation happens through three steps: ► Filtration removes waste and some useful substances from the blood. ► Reabsorption takes back useful substances like water and glucose. ► Secretion adds more waste into the urine. And all of this is controlled by hormones like ADH and aldosterone to help the body stay balanced. Urine Formation Video Urine Formation https://www.youtube.com/watch?v=9_h0ZXx1lFw Micturition https://www.youtube.com/watch?v=US0vNoxsW-k 1.Filtration ► This takes place through the semi permeable walls of the glomerulus and the glomerular capsule. ► Water and small molecules pass through here. ► Blood cells, plasma proteins and other large molecules cannot pass through, due to size and therefore remains within the capillaries. ► Filtration needs to take place because there is a difference between the blood pressure in the glomerulus and the pressure of the filtrate in the glomerular capsule because the efferent arteriole is narrower than the afferent arteriole. Filtration ► The volume of filtrate formed by each kidney, each minute is called Glomerular Filtration Rate (GFR). ► In all healthy adults the GFR is about 125ml/min. That is 180 liters of filtrate are formed each day by the two kidneys. ► The filtrate is later reabsorbed from the kidney tubules with less than 1%, this is about 1- 1.5liters, excreted as Urine. ► Autoregulation: Renal blood flow and glomerular filtration is protected by a mechanism called Autoregulation. Autoregulation is independently of Nervous Control. Filtration ► If the nerve supply to the renal blood supply is interrupted, auto regulation continues to operate. ► It is therefore a property inherent in renal blood vessels, it may be stimulated by changes in blood pressure in the renal arteries. ► In severe shock, when the systolic blood pressure falls below 80mmhg, autoregulation fails. 2. Selective Reabsorption ► Most Reabsorption from the filtrate into the blood takes place in the Proximal Convoluted Tubule, whose walls are lined with microvilli to increase surface area for absorption. ► Many substances are reabsorbed here, including some water, electrolytes and organic nutrients such as glucose. ► Only 60-70% of filtrate reaches the medullary loop. ► Especially water, sodium and chloride, is reabsorbed in the loop. ► Therefore this means that only 15-20% of the original filtrate reaches the distal convoluted tubule. Selective Reabsorption ► The filtrate that enters the collecting ducts are dilute. ► The collecting ducts function is to for the reabsorption of water as much as the body needs. ► Glomerular filtrate (e.g Glucose, amino acids) do not normally appear in the urine because they are completely reabsorbed unless blood levels are excessive. ► Reabsorption of urea, uric acid and creatinine is very limited. ► The kidneys’ maximum capacity for the reabsorption of a substance is called the Transport Maximum or Renal Threshold. Selective Reabsorption Hormones that influence Selective Reabsorption: ► Parathyroid Hormone This is secreted by the parathyroid gland and together with calcitonin from the thyroid regulates the reabsorption of Calcium, and Phosphate from the distal collecting tubules so that normal blood levels are maintained. Parathyroid hormone increases the blood calcium level and calcitonin lowers it. ► Antidiuretic Hormone (ADH): This is secreted by the posterior pituitary gland. It increases the permeability of the distal convoluted tubule and collecting tubules, increasing water reabsorption. Selective Reabsorption ► Aldosterone This is secreted by the adrenal cortex, this hormone increases the reabsorption of sodium and water and the excretion of potassium. ► Atrial Natriuretic Peptide (ANP) This is secreted by the atria of the heart. It decreases reabsorption of sodium and water from the proximal convoluted tubules and collecting ducts. Tubular Secretions ► Substances are not required and foreign materials e.g drugs like penincillin, and aspirin, may not be entirely filtered out of the blood because of the short time it remains in the glomerulus. ► Such substances are cleared by secretion from the peritubular capillaries into the filtrate within the convoluted tubules. Urine ► After production of Urine, it is drained from the Renal pelvis by the ureters to flow into the bladder. ► The bladder then stores the urine until it is voided through the urethra. ► If waste products are allowed to accumulate they become poisonous, a condition called Uremia. Anatomy & Physiology of Renal System Kidneys Location ► Posterior abdominal wall, one on each side of the vertebral column, behind the peritoneum and below the diaphragm. ► It extends at the level of the 12th Thoracic Vertebra and 3rd Lumbar Vertebra. ► It receives some protection from the lower rib cage. Kidneys Structure ► Bean shaped, 11cm Long, 6cm Wide and 3 cm thick and weighs about 150 grams. There are 3 areas of Tissue: 1. An outer fibrous capsule surrounding the kidney. 2. The Outer cortex - reddish brown layer of tissue below the capsule and outside the renal pyramid 3. The Medulla – the innermost layer consisting of conical shaped, renal pyramids. The kidney has a depression on the medial side where the renal artery enters the kidney and renal vein and the ureter exit the kidney. The depression is called the Hilum. Kidneys ► The hilum is the concave medial border of the kidney, where the renal blood and the lymph vessels, the ureter and nerves enter. ► Urine formed within the kidney passes through a renal papilla at the apex of the pyramid into a minor calyx ► Several minor calyces merge into a major calyx and two or three major calyces combine forming the renal pelvis. ► The renal pelvis is a funnel shaped structure that narrows when it leaves the kidney as the ureter. Diagram of Coronal Section of Kidney & Details of the Renal Pyramid Blood flow through the Kidney ► The Kidney filters material from the blood and returns important materials such as water, glucose, and sodium back to the blood. ► The arterial system takes blood to the cortex of kidney and several capillary beds. ► The venous system returns blood to the inferior vena cava. Blood flow through the Kidney Composition of Urine ► Urine is clear to amber in color, due to the presence of Urobilin (a bile pigment) ► It is made up of 95-96% of water and 2% Urea. ► It consists of Uric Acid, Creatinine, Ammonia, Sodium & Potassium. These account for 2% of urine composition. References ► Wise, Eric.2015.Anatomy Physiology: The Unity of Form and Function.(Seventh Edition). McGraw-Hill Education Publishing. ► Engelkirk, Paul G., Engelkirk, Janet Duben. 2015. Burton’s Microbiology for the Health Sciences. (Tenth Edition). Lippincott-Williams & Wilkins. The End Questions or Clarifications?