BIO 241 1st Edition Lecture 23 Outline of Current Lecture I. ExcretionII. Introduction to the urinary systemIII. External anatomy of the kidneyIV. Internal anatomy of the kidneyV. NephronVI. Endothelial-capsular membraneVII. Renal tubule histology Current LectureI. Excretion differs significantly from secretion. Secretion is putting something on a body’s surface such as the pancreas secreting pancreatic enzymes. Excretion is purposefully getting something out of the body such as feces or urine. We need a urinary system because protein catabolism yields toxic nitrogenous waste. NH3 is converted to ammoniawhich becomes urea. Creatinine and uric acid also form. Water and essential ions tend to accumulate so the urinary system reabsorbs these things. Kidneys, lungs, GI tract, andsudoriferous glands are organs that contribute to waste elimination. II. The urinary tract consists of two kidneys, two ureters (connects kidneys to bladder), a urinary bladder, and one urethra (what you urinate out of). The general functions of the kidneys are to regulate blood volume and composition, regulate blood pressure with renin, regulate RBC numbers with erythropoietin, and synthesize vitamin D (calcitriol). III. The external anatomy of the kidneys are posteriorly located on the body wall from T12-L3. The kidneys have three coverings that consist of the renal fascia, adipose capsule, and renal capsule shown below.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.IV. The internal anatomy consists of the renal cortex, renal medulla, and renal sinus. Within the cortex are renal columns (lighter shade) and nephrons (functional unit of kidney; about 1 million). The medulla gathers urine via the renal pyramids and renal papillae (“little hill”). The sinus is the space where the tubes open up. The renal pelvis has 5-9 minor calyces and 2-3 major calyces. These aid in the collection of urine. They are shown below.V. Nephrons are the functional cells of the kidneys. They filtrate, reabsorb, and secrete things to aid in the excretion process. 85% of nephrons are cortical nephrons, meaning they are locatedin the cortex, and have short loops of Henle. 15% are juxtmedullary and they have a long loop of Henle. There are two subdivisions within a nephron. The first is the renal corpuscle which consists of the glomerulus (capillary bed within bowman’s capsule) and the Bowman’s capsule which has a parietal and visceral layer. The other subdivision is the renal tubule. It follows the following pattern: proximal convuluted → proximal straight → loop of Henle → distal convuluted → distal straight. These are shown below.VI. Because the Bowman’s capsule has two layers, it creates a capsular space similar to the pericardium. This helps create the endothelial-capsular membrane which consist of a fenestrated endothelium (restricts formed elements), fused basement membrane (restricts plasma proteins), and a visceral layer made of podocytes. These are very unique cells of the body. They have pedicels, which are feet-like structures, and filtration slits. This is shown below.VII. The renal tubule histology is as follows: proximal tubule = simple cuboidal + brush border, loop of Henle = simple squamous, distal tubule = simple cuboidal + basal foldings, and collectingducts = simple
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