Chapter 8 Chapter 8 Renal Physiology Physiology department Shenyang Medical College

Department of physiology Shenyang Medical College2 Introduction The process that the cellular waste products or extra nutrients 、 minerals and water leaving the body through the blood circulation. Excretion:

Department of physiology Shenyang Medical College3 Four excretory pathways 4. By kidney 1. By respiratory organ 2. By intestinal tract, defecation is not excretion. 3. By skin

Department of physiology Shenyang Medical College4 The functional significance of excretion The functional significance of excretion 4. Reservation of important materials in body fluid such as Na + 、 K + 、 HCO 3 - and Cl Elimination of waste products and foreign materials. 2. Elimination of extra electrolyte 、 H + so to maintain acid-based balance. 3. Regulation of extracellular fluid and osmotic pressure in blood.

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15 UROSIS Section 1 Renal functional anatomy and renal blood flow

Department of physiology Shenyang Medical College16 Functions of the Kidney 1. Urine formation(Excretion) 2. To maintain constancy of internal environment. 3. Endocrine functions: A. Erythropoietin, EPO B. Rennin C. VitD3

Department of physiology Shenyang Medical College17 Physiologic anatomy The compositions of nephron The nephron is the functional unit of the kidney. There are have 1 million nephron/each kidney, each capable of forming urine.

Department of physiology Shenyang Medical College18 1. The kidney cannot regenerate new nephrons. Therefore, with renal injury, disease, or normal aging, there is a gradual decrease in nephron number. 2. After 40 ages, nephrons can decrease 10 per cent/year. 3.Upping 80 years old, many people have 40 per cent fewer functioning nephrons than they did not at age 40.

Department of physiology Shenyang Medical College19 1. Each nephron including glomerulus, which encased in Bowman`s capsule, and renal tubule. 2. Renal tubule compositions of three parts, there are proximal tubule, loop of Henle and distal tubule. 3. Loop of Henle consists of thin segment of descending limb, thin segment of ascending limb and thick segment of ascending limb.

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Department of physiology Shenyang Medical College22 How Do Kidneys Work ?Work

Department of physiology Shenyang Medical College23 Process of three basic urosis The nephron and collecting tubule are together forming the urine. It is including three basic processes: 1.glomerular filtration 2.reabsorption of substances from the renal tubules into the blood 3.secretion of substances from the blood into the renal tubules

Department of physiology Shenyang Medical College25 Micturition Nephron →→ collecting tubule →→ minor calyx →→ major calyx →→ pelvis →→ ureter →→ urinary bladder →→ urethra Urine ( excretion ) = filtration – reabsorption + secretion

Department of physiology Shenyang Medical College26 Regional differences in nephron structure Cortical nephrons Juxtamedullary nephrons

Cortical nephron Juxtamedullary nephron

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Cortical nephronJuxtamedullary nephron Site Glomeruli located in the outer cortex Lie deep in the renal cortex near the medullary Number 85 ~ 90 per cent10 ~ 15 per cent Volume smalllarge Ratio in afferent and efferent arterioles 2 : 11 : 1 Vasa recta nohave Loops of Henle Short,penetrate only a short distance into medulla Long dip deeply into the medulla, in same cases all the way to the tips of the renal papillae FunctionurosisForming of concentrated urine Macula densa YN

Cortical nephron and Juxtamedullary nephron Cortical nephron and Juxtamedullary nephron

Department of physiology Shenyang Medical College31 C. the extraglomerular mesangium cell Juxtaglomerular apparatus (1) Component : A. the juxtaglomerular cells B. the macula densa

Juxtaglomerular apparatus

Department of physiology Shenyang Medical College33 It is at the beginning of distal convoluted tubule. The function of the macula densa is to monitor the concentration of sodium chloride in the tubular fluid and transfer the information to juxtaglomerular cells, there regulate the release of rennin. (2) FunctionFunction A. The juxtaglomerular cells They are specialized myoepithelial cells in the media of afferent arteriole, the cells release rennin. B. The macula densa

Department of physiology Shenyang Medical College34 Renal blood vessel distribute Two capillary beds High hydrostatic pressure in the glomerular capillaries, about 60 mmHg, cause rapid fluid filtration. Much lower hydrostatic pressure in the peritubular capillaries, about 13 mmHg, permits rapid fluid reabsorption.

Renal blood flow

Department of physiology Shenyang Medical College38 Renal blood flow Renal Blood Supply is normally is about 20% of the cardiac output, about 1200 ml/min. 94% of the blood flow goes to the cortex, 5%-6% of the blood flow goes to the outer medulla <1% of the blood flow goes to the inner medulla.

(1) Autoregulation of renal blood flow

Department of physiology Shenyang Medical College40 the blood flow relatively constant a.Myogenic mechanism Arterial blood pressure contraction of the afferent arteriolar smooth muscle contraction of the afferent arteriolar

Department of physiology Shenyang Medical College41 Blood Flow = Capillary Pressure / Flow resistance 1) Myogenic Mechanism of the autoregulation

Department of physiology Shenyang Medical College42 b.Tubuloglomerular feedback, TCF Tubuloglomerular feedbackTubuloglomerular feedback When the RBF increasing →→ reaching the distal tubule [ Na + ] ↑ →→ Macula Densa feedback →→ →→ →→ glomeruli →→ contraction of afferent arterioles smooth muscle →→ RBF returning normal.

Department of physiology Shenyang Medical College45 renal blood flow and glomerular filtration rate (GFR) Neuro-humoral contral (1)Neural regulaion of the renal blood flow Renal sympathetic nervous(+) constriction of the renal arterioles

Department of physiology Shenyang Medical College46 Nitric Oxide (2) Humoral regulaion of the renal blood flow Norepinephrine, Epinephrine and Endothelin constriction of the renal arterioles and GFR Angiotensin Ⅱ, constrict efferent arterioles Renal vascula resistance and GFR Prostaglandins I 2/ E 2 and Bradykinin Tend to increase GFR