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1. THE EXCRETORY SYSTEM By: Mrs.Keerthi.K Asst.Professor Vijay Marie CON

2. INTRODUCTION Renal system includes: 1. A pair of kidneys 2. Ureters 3. Urinary bladder 4. Urethra . Once the kidneys filter the blood plasma, they return most of the water and solutes to the blood stream. The remaining water and solutes constitute URINE which passes through ureters and is stored in bladder until it is excreted from body through urethra. NEPHROLOGY: scientific study of anatomy , physiology and pathology of kidneys . Nephrologists are focused on medical, non-surgical treatment of kidney disorders. UROLOGY : branch of medicine that deals with male and female urinary Urologists are surgeons who treat both urinary tract disorders and male reproductive system issues, often through surgical intervention.

3. Urinary System The Urinary system is the main excretory system of the body,which expel the waste and excess material form the body. The urinary System is also known as Excretory System or Renal System Excretion: Excretion is the process by which the unwanted substances and metabolic wastes are eliminated from the body. A large amount of waste materials and carbon dioxide are produced in the tissues during metabolic process. In addition, residue of undigested food, heavy metals, drugs, toxic substances and pathogenic organisms like bacteria are also present in the body. All these substances must be removed to keep the body in healthy condition. Various systems/organs in the body are involved in performing the excretory function, viz . Although various organs are involved in removal of wastes from the body, their excretory capacity is limited. But renal system or urinary system has maximum excretory capacity and so it plays a major role in homeostasis .

4. FUNCTIONS OF KIDNEYS

5. 1. BLOOD IONIC COMPOSITION Regulates the levels of several ions , mostly Na+,ca+2,cl-,Hpo4- 3. REGULATION OF BLOOD VOLUME: Kidneys adjust blood volume by conserving or eliminating water in urine. Increase in blood volume increases blood pressure and decrease in blood volume decreases blood pressure. FUNCTIONS OF KIDNEYS 2.REGULATION OF BLOOD PH: They excrete a variable amount of H+into the urine and conserve Hco3- which is an important buffer of H+ ion balance. Both these activities helps to regulate PH

6. 4. REGULATION OF BP: Renin-Angiotensin-Aldosterone System (RAAS ) : They secrete renin a hormone which activates Renin-Angiotensin-Aldosterone pathway. Increased renin causes increased BP 6.PRODUCTION OF HORMONES: 1.CALCITRIOL: active form of vitamin D that regulates calcium homeostasis. 2. ERYTHROPOIETIN: helps in production of RBC’s. FUNCTIONS OF KIDNEYS 5.MAINTAIN BLOOD OSMOLARITY By separately regulating loss of water and loss of solutes in urine. Kidneys maintain blood osmolarity to 300 mosm /lit.

7. 7. REGULATION OF BLOOD GLUCOSE LEVELS: Like liver , kidneys can use amino acid glutamine in gluconeogenesis which releases glucose into blood to maintain normal blood glucose levels. 8. EXCRETION OF WASTES AND FOREIGN SUBSTANCES: By forming urine kidneys help excrete wastes. Some wastes are formed from metabolic reactions in body- NH4 and urea( from deamination of aminoacids ). BILIRUBIN: from catabolism of hemoglobin. CREATININE: breakdown of creatinine phosphate in muscle fibers. URIC ACID: catabolism of nucleic acids. OTHER WASTES: metabolism of diet , drugs and environmental toxins FUNCTIONS OF KIDNEYS

8. GROSS APPEARANCE : paired, reddish and bean shaped. LOCATION : located just above the waist between peritoneum and posterior wall of abdomen. Because their position is posterior to peritoneum of abdominal cavity – hence they are called RETROPERITONEAL ORGANS. Located between levels of last thoracic and 3 rd lumbar vertebrae protected by 11 th and 12 th pair of ribs. Right kidney is slightly lower than the left because of the presence of liver ANATOMY OF KIDNEYS

9. LENGTH : 10-12cms WIDTH : 5-7cms THICKNESS: 3cms and size of bar soap WEIGHT: 135-150grams THE CONCAVE BOARDER: faces the vertebral column. Near the center of the concave boarder there is an indentation called HILUM/RENAL HILUS through which ureter emerges along with blood vessels, lymphatic vessels and nerves. ANATOMY OF KIDNEYS-EXTERNAL

10. ANATOMY OF KIDNEYS-EXTERNAL

11. A frontal section through kidney reveals 2 distinct regions: RENAL CORTEX- superficial light red area RENAL MEDULLA – darker reddish brown inner region The renal medulla consists of several cone shaped structures- RENAL PYRAMIDS . BASE of renal pyramids – faces renal cortex APEX – is called RENAL PAPILLA –points towards renal hilum. INTERNAL ANATOMY OF KIDNEYS

12. A frontal section through the kidney reveals an outer region called the  renal cortex  and an inner region called the  renal medulla  ( Figure 25.1.2 ). In the medulla, 5-8  renal pyramids  are separated by connective tissue  renal columns.  Each pyramid creates urine and terminates into a  renal papilla.  Each renal papilla drains into a collecting pool called a  minor calyx ; several minor calyces connect to form a  major calyx ; all major calyces connect to the single renal pelvis which connects to the urete INTERNAL ANATOMY OF KIDNEYS

13. RENAL LOBE: Renal Pyramid+ overlying area of renal cortex+ half of each adjacent renal column. Together ,the renal cortex and renal pyramids of renal medulla- RENAL PARENCHYMA or the functional portion of kidney. Within the parenchyma , millions of functional units of kidneys called NEPHRONS are present. Filtrate formed from nephrons drains into large papillary ducts and then into large cup shaped structures called minor and major calyces. INTERNAL ANATOMY OF KIDNEYS

14. Each kidney has 8-18 minor calyces and 2-3 major calyces. Minor calyx receives urine from papillary duct of one real papilla and delivers it to a major calyx. Once the filtrate enters calyces it becomes urine as further reabsorption doesnot occur INTERNAL ANATOMY OF KIDNEYS

15. BLOOD SUPPLY TO KIDNEYS

16. Kidneys are abundantly supplied with blood vessels In adults renal blood flow is 1200ml/min Within the kidney the renal artery divides into several SEGMENTAL ARTERIES. Each segmental artery gives off several branches that enter расенсута b/w renal pyramids and pass through renal columns as INTERLOBAR ARTERIES. At the base of renal pyramid. the interlobar arteries arch between renal medulla & content= hence called as ARCUATE –ARTERIES Division of arcuate arteries produce a series of INTERLOBULAR ARTERIES - They pass between lobules into Afferent arterioles. BLOOD SUPPLY TO KIDNEYS

17. Each nephron receives one afferent arteriole which divides into a tangled ,ball shaped capillary network called GLOMERULUS. The glomerular capillaries reunite to form efferent arteriole that carries blood out of glomerulus. The efferent .A divides to form Peritubular capillaries BLOOD SUPPLY TO KIDNEYS

18. BLOOD SUPPLY TO KIDNEYS

19. Nephron- Function Of Renal Tubules Nephron Definition “Nephron is the basic functional unit of kidneys that consists of a glomerulus and its associated tubules through which the glomerular filtrate passes before it emerges as urine” What is Nephron? A nephron is the basic structural and functional unit of the kidney. They are the microscopic structure composed of a renal corpuscle and a renal tubule. The word nephron is derived from the Greek word –  nephros , meaning kidney. There are about millions of nephrons in each human kidney. THE NEPHRON

20. The mammalian nephron is a long tube-like structure, its length varying from 35–55 mm long. At one end, the tube is closed, folded and expanded, into a double-walled, a cuplike structure called the Bowman’s capsule or renal corpuscular capsule,  which encloses a cluster of microscopic blood vessels called the glomerulus. This capsule and glomerulus together constitute the renal corpuscle . The structure of nephron comprises two major portions: Renal Tubule Renal Corpuscle Structure of Nephron

21. Renal Tubule The renal tubule is a long and convoluted structure that emerges from the glomerulus and can be divided into three parts based on function. The first part is called the proximal convoluted tubule (PCT) due to its proximity to the glomerulus; it stays in the renal cortex. The second part is called the loop of Henle , or nephritic loop because it forms a loop (with descending and ascending limbs) that goes through the renal medulla. The third part of the renal tubule is called the distal convoluted tubule (DCT) and this part is also restricted to the renal cortex. Structure of Nephron

22. Renal Tubule Conti… The capillaries of the glomerulus are enclosed by a cup-like structure called Bowman’s capsule. This structure extends to form highly coiled tubules called PCT. PCT continues to form the loop of Henle which ascends to DCT, which in turn opens into the collecting duct. The major function of tubules is reabsorption and the process can either be through  active transport  or passive transport. In addition, secretions by tubules help in the urine formation without affecting the electrolyte balance of the body . Proximal Convoluted Tubule (PCT) The blood brought by the renal artery is filtered by the glomerulus and then passed to the PCT. Maximum reabsorption takes place in PCT of the nephron.PCT is the region of renal tubule where reabsorption of essential substances like glucose, proteins, amino acids, a major portion of electrolytes and water takes place. The surface area for reabsorption is facilitated by the lining of the simple cuboidal epithelium in them. Reabsorption takes place at the expense of energy, i.e., the process is active.PCT selectively secretes ions such as hydrogen, ammonia, and potassium into the filtrate and absorbs HCO 3 – from it. Thus, PCT maintains the electrolyte and acid-base balance of the body fluids.

23. Renal Tubule Conti… Henle’s Loop Henle’s loop has a descending and an ascending limb. Being parts of the same loop, both the descending and ascending limbs show different permeability. The descending limb is permeable to water but impermeable to an electrolyte, while the ascending limb is permeable to electrolytes but impermeable to water. Since the electrolytes get reabsorbed at the ascending loop of Henle , the filtrate gets diluted as it moves towards the ascending limb. But reabsorption is limited in this segment. Distal Convoluted Tubule (DCT) The DCT, which is the last part of the nephron, connects and empties its contents into collecting ducts that line the medullary pyramids. The collecting ducts amass contents from multiple nephrons and fuse together as they enter the papillae of the renal medulla. Similar to PCT, DCT also secretes ions such as hydrogen, potassium, and NH 3  into the filtrate while reabsorbing the HCO 3 – from the filtrate. Conditional reabsorption of sodium ions and water takes place in DCT. Thus, it maintains the pH and sodium-potassium level in the blood cells . Collecting Duct Collecting duct is a long, straight tube where H+ and K+ ions are secreted to maintain the electrolyte balance of the blood. This is also the region where the maximum reabsorption of water takes place to produce concentrated urine.

24. Renal Corpuscle Renal Corpuscle The renal corpuscle consists of a glomerulus surrounded by a Bowman’s capsule. The glomerulus arises from an afferent arteriole and empties into an efferent arteriole. The smaller diameter of an efferent arteriole helps to maintain high blood pressure in the glomerulus. The Bowman’s capsule is divided into three layers: Outer Parietal layer:  It is made up of epithelial cells with minute pores of diameter 12nm. Middle Basement membrane:  This layer is selectively permeable. Inner Visceral Layer:  It consists of large nucleated cells called podocytes which bear finger-like projections called podocel .

25. 2.RENAL TUBULE: there are 2 main sections Proximal convoluted tubule (PCT) Loop of Henle (LOH) Distal Convulued tubule (DCT) PCT denotes a part of tubule attached to Glomerular capsule . Distal denotes the part that is farther away . Convoluted means tubule is tightly coiled THE NEPHRON

26. Renal corpuscle and both CT’s lie within the renal cortex, whereas LOH extends into renal medulla , make a hairpin turn and returns to renal cortex. The DCT of several nephrons empty into a single collecting duct. Collecting ducts unite and converge into several hundreds papillary ducts that drain into minor calyces. In a nephron the LOH connects PCT and DCT. The first part of LOH dips into the renal medulla, where it is called descending limb of LOH. It makes a hairpin turn and returns to renal cortex as the ascending limb of LOH. THE NEPHRON

27. CORTICAL NEPHRONS About 80-85%. Their renal corpuscles lie in outer portion of renal cortex. They have short LOH that lie in cortex and penetrate only into the outer region of renal medulla. JUXTRA-MEDULLARY NEPHRONS The other 15-20%. Their renal corpuscles lie deep in the cortex, close to medulla. They have long LOH that extends into the deepest region of medulla. These nephrons have 2 additional portions: Thin ascending LOH Thick ascending LOH THE NEPHRON-TYPES

28. VISCERAL LAYER: modified SSE cells called PODOCYTES. The many foot like projections of these cells wrap around a single layer of endothelial cells of glomerular capillaries and form inner wall of capsule. PARIETAL LAYER: Consists of SSE and forms outer wall of capsule. Fluid filtered from glomerular capillaries enters capsular space (the space between 2 layers of glomerular capsule) THE NEPHRON A single layer of epithelial cells forms the entire wall of the glomerular capsule , renal tubule and ducts. However each part has distinctive histological features and reflect its articular functions: 1.GLOMERULAR CAPSULE: 2 layers

29. IN PCT: Simple cuboidal cells with prominent brush boarder of microvilli on their apical surface. These microvilli increase surface area of reabsorption and secretion. Descending limb of LOH and 1 st part of thin AL of LOH –simple squamous epithelium. Thick ascending limb of LOH- simple cuboidal to low columnar epithelium. RENAL TUBULE AND COLLECTING DUCT

30. In the renal corpuscle –the columnar tubule cells are crowded and are called as MACULA DENSA. The site where the A/L touches the afferent arteriole – specialized cells (cuboidal cells are crowded ) called macula densa . Only in macula densa area the aff.arteriole has JG cells. Along side of macula densa the wall of afferent arteriole contains modified smooth muscle fibers called JUXTRA GLOMERULAR CELLS. Together with macula densa + JG cells= JG apparatus- very sensitive to Na+and Cl- reabsorption RENAL TUBULE AND COLLECTING DUCT

31. There are two types of cells: PRINCIPAL CELLS: receptors for ADH and aldosterone INTERCALATED CELLS: homeostasis of blood PH DCT

32. Each of 2 ureters transports urine from renal pelvis to the bladder. Peristalisis contractions of the muscular walls of the ureters push urine towards the bladder, but the hydrostatic pressure and gravity also contribute . Frequency of peristalitic waves – 5/min. LENGTH- 25-30cms DIAMETER- 1mm-10mm RETROPERITONEAL URETERS

33. There is no anatomical valve at the opening of each ureter , into bladder , a physiological one is quiet effective. As the bladder fills , pressure with in compresses the oblique openings into ureters and prevents backflow of urine. If the physiological valve is not functioning then the microbes travel upto the ureter from bladder to infect both kidneys. URETERS

34. MUCOSA WITH UNDERLYING LAMINA PROPRIA MUSCULARIS ADVENTITIA Deepest , lined with transitional epithelium and goblet cells. Lamina propria is the areolar connective tissue with collagen, elastic fibers and lymphatic tissue Middle layer INNER- Longitudinal OUTER- circular helps in peristalsis. Transitional epithelium is able to stretch- stretches to accommodate urine. Mucous secreted by goblet cells prevents cells of mucosa to come in contact with urine. Superficial layer- areolar connective tissue with blood vessels, lymphatic vessels and nerves that serves muscularis and mucosa. URETERS-LAYERS

35. It is hollow , distensible muscular organ situated in pelvic cavity posterior to the pubic symphysis. In males, it is anterior to rectum, in females it is anterior to vagina and inferior to uterus . Folds of peritoneum holds bladder in position. SHAPE: spherical –when slightly distended due to accumulation of urine. When it is empty , it collapses . As urine volume increases it becomes pear shaped and rises into the abdominal cavity. URINARY BLADDER

36. Capacity-700-800ml It is smaller in females because the uterus occupies the space just as superior to urinary bladder. URINARY BLADDER

37. In the floor of bladder there is small triangular area called the ‘TRIGONE’ Posterior corners of trigone- has 2 ureteral opening and 1 urethral opening called internal urethral orifice. 3 coats makeup the wall of urinary bladder. URINARY BLADDER-ANATOMY&HISTOLOGY

38. 1.MUCOSA: deepest made of transitional epithelium + underlying lamina propria similar to that of ureters. RUGAE- are also present to permit the expansion of bladder. Surrounding mucosa there is intermediate MUSCULARIS or DETRUSOR MUSCLE- 3 layers of smooth muscles. Inner longitudinal muscle Middle circular muscles Outer longitudinal muscles URINARY BLADDER-ANATOMY&HISTOLOGY

39. Around the opening to the urethra the circular fibers form an IU sphincter inferior to it there is external urethral sphincter composed of skeletal muscle. 3.ADVENTITIA: most superficial layer Areolar connective tissue Over superior surface of urinary bladder is SEROSA layer of visceral peritoneum. URINARY BLADDER-ANATOMY&HISTOLOGY

40. A tubular structure emerging from the neck of the bladder and opens to the exterior. It is the outlet of the bladder and eliminates urine to outside. Present in both males and females but there are some differences between the two. URETHRA

41. MALE URETHRA FEMALE URETHRA Long Short Length = 18-20cms Length =4cms Function: urination and ejaculation of semen Only urination Course – curved (double) Nearly straight –foleys catheterization is easy. DIFFERENCES BETWEEN MALE AND FEMALE URETHRA

42. MALE URETHRA FEMALE URETHRA Long Short Length = 18-20cms Length =4cms Function: urination and ejaculation of semen Only urination Course – curved (double) Nearly straight –foleys catheterization is easy. PARTS OF URETHRA