1. Chapter 26: The Urinary System
BIO 211 Lab
Instructor: Dr. Gollwitzer

2. Today in class we will:
Identify the major function of the urinary system
Identify the major components of the urinary system and their functions
Trace the path of filtrate/urine through the urinary system
Begin our discussion on the organs and anatomical structures of the urinary system:
Kidneys
Gross anatomy
Position
Sectional anatomy
Renal flow
Blood supply and blood flow

3. Introduction Major function: 2 major components:
To excrete waste products
2 major components:
Kidneys:
Produce urine =
Fluid containing water, ions, small soluble compounds and toxic substances
Urinary tract:
Transports and stores urine prior to elimination
Consists of:
Ureters – paired tubes from the kidney to the bladder
Urinary bladder – muscular sac for temporary storage of urine
Urethra – from bladder to exterior
Kidneys  urine  ureters  urinary bladder  urethra  exterior

4. Figure 26-1

5. Figure 26-3

6. Kidneys: Gross Anatomy
Paired organs on either side of vertebral column; left slightly superior to right
Reddish-brown, kidney-bean shaped
Adrenal glands on superior surface
Approximate size of hand
Hilum = depression where blood vessels (renal artery and vein) and lymphatic vessels, nerves, and ureter pass into/out of kidney

7. Figure 26-2a

8. Kidneys: Position Retroperitoneal (“behind”):
Between muscles of dorsal body wall and parietal peritoneum
Behind parietal peritoneum of abdominal cavity in retroperitoneal space; separated by parietal peritoneum
Position in abdominal cavity maintained by:
Overlying peritoneum
Contact with adjacent visceral organs
3 concentric layers of supportive CT

9. Figure 26-2b

10. Kidney: CT layers
Renal capsule – tough layer of collagen fibers, covers outer surface of kidney
Adipose capsule – thick middle layer, surrounds renal capsule; cushions kidney
Renal fascia – dense, fibrous outer layer (also surrounds adrenal gland)
Anchors kidney to surrounding structures
Fuses with deep fascia (surrounding muscles of body wall) and peritoneum
When renal fascia torn  floating kidney
Dangerous because of potential twisting/kinking of ureters and blood vessels

11. Kidney: Sectional Anatomy
Renal cortex – outer layer in contact with renal capsule; appears grainy
Renal columns – bands of cortical tissue that extend into renal medulla and separate renal pyramids
Renal medulla:
Inner layer adjacent to renal cortex; looks like strands of combed hair
Consists of 6 – 18 renal pyramids (triangular structures)
Base of each pyramid in contact with cortex
Tip forms renal papilla
Striations = loops of Henle and collecting ducts of nephrons (functional units of kidney)
Ducts discharge urine in to cup-shaped minor calyx

12. Kidney
Figure 26-4, a,b

13. Kidney: Sectional Anatomy
Renal lobe:
Functional component where urine production occurs
Consists of:
Renal pyramid +
Overlying renal cortex +
Adjacent renal columns
Note: Think 3D – visualize handful of waffle cones = Kidney
Ice cream = cortex
Cone = medulla
Paper around each cone = renal columns

14. Kidney: Renal Flow
Renal papillae from several renal pyramids discharge into a minor calyx
4-5 minor calyces discharge into a major calyx
2-3 major calyces form the renal pelvis =
Large funnel-shaped chamber that fills most of renal sinus and connects to ureter

15. Kidney
Renal sinus = internal cavity lined by inner surface of renal capsule

16. Nephrons Microscopic, tubular structures in cortex of renal lobe
Functional/filtration unit of kidney = where urine production begins
Approx million/kidney
Consists of:
Renal corpuscle = filtering body
Renal tubule (equivalent to 85 miles) = urine collecting and concentrating tube

17. Figure 26-6, 7th edition

18. Kidney: Renal Corpuscle
Round structure consisting of:
Glomerulus
Bowman’s capsule

19. Kidney: Renal Corpuscle
Glomerulus
Ball of intertwined fenestrated capillaries (approx. 50)
Parietal and visceral epithelia separated by capsular space
Visceral epithelium
Covers glomerular capillaries
Consists of podocytes (= large simple squamous cells) with “feet” = pedicels
Narrow gaps between adjacent pedicels = filtration slits – allow filtrates to enter Bowman’s capsule

20. Kidney: Renal Corpuscle
Bowman’s capsule
Cup-shaped body
Encircles glomerular capillaries
Collects filtrate forced out of capillaries in capsular space
Connected to initial segment of renal tubule

21. Kidney: Renal Corpuscle
Blood arrives at renal corpuscle via afferent arteriole and leaves via efferent arteriole
In renal corpuscle, BP forces fluid and dissolved solutes out of glomerular capillaries (fenestrated) into capsular space (between glomerulus and capsule) = filtration  protein-free solution (filtrate)

22. Figure 26-8

23. Kidney: Renal Tubule
Filtrate (tubular fluid) leaves renal corpuscle and enters renal tubule
Has 3 sections:
2 coiled/twisted segments (located in the cortex)
Separated by a U-shaped tubule (located partially or completely in the medulla)

24. Kidney: Renal Tubule Proximal convoluted tubule (PCT): Loop of Henle:
First segment that exits Bowman’s capsule in
Entrance opposite afferent/efferent arterioles
Loop of Henle:
Descending limb (turns toward renal medulla)
Ascending limb (turns toward cortex)
Distal convoluted tubule (DCT):
Passes between afferent and efferent arterioles
Empties into collecting duct in cortex

25. Figure 26-6, 7th edition

26. Kidney: Renal Tubule
Tubular fluid changes in composition as it travels through each segment of the nephron
Reabsorption of:
Useful organic compounds (glucose, fatty acids, amino acids, vitamins etc)
Ions (Na, K)
Water (>90%) from tubular fluid and release them into the peritubular fluid –
Secretion of waste products missed by filtration

27. Kidney: Juxtaglomerular Apparatus (JGA)
Located where DCT and afferent arteriole are in close contact with each other and the renal corpuscle
Formed by:
JG cells
Macula densa
An endocrine structure that secretes:
Hormone erythropoietin
In response to low O2
Primary function
Enzyme renin:
Elevates BP and Na retention

28. Figure 26-8

29. Kidney: Types of Nephrons
Nephrons from different locations differ in structure
Cortical nephrons (85%) – in superficial cortex:
Short loop of Henle; descends only slightly into renal medulla
Efferent arteriole delivers blood to peritubular capillaries which surround entire renal tubule and drain into small venules  interlobular veins
Juxtamedullary nephrons (15%) – near medulla:
Long loop of Henle extends deep into medulla
Peritubular capillaries connected to vasa recta = long, straight capillaries that parallel the loop of Henle

30. Figure 26-7
Figure 26–7

31. Kidney: Collecting System
Collecting duct:
Receives tubular fluid from DCT of several nephrons
Begins in cortex and ends in medulla (at papillary duct)
Papillary duct:
Receives fluid from several collecting ducts
Drains into minor calyx

32. Blood Supply to Kidneys
Major function of kidneys is to filter blood
Therefore, large volumes of blood delivered to kidneys (almost 20 gallons/hr!)
Blood flow:
Abdominal aorta  renal artery  segmental artery  interlobar artery  arcuate artery  interlobular artery  afferent arteriole  renal corpuscle glomerulus  efferent arteriole 
For cortical nephrons:
 peritubular capillary  venule  interlobular vein
For juxtamedullary nephrons:
 peritubular capillary  vasa recta  venule  interlobular vein
Interlobular vein  arcuate vein  interlobar vein  segmental vein  renal vein

33. Figure 26-5

34. Today in class we will:
Continue our discussion on the organs and anatomical structures of the urinary system:
Urinary tract
Ureters
Urinary bladder
Urethra
Female
Male
Renal flow
Blood supply

35. Urinary Tract Consists of: paired ureters, urinary bladder, urethra
Responsible for urine transport, storage, and elimination
Ureters:
Pair of muscular tubes from kidney renal pelvis to urinary bladder
Penetrate posterior, inferior wall of bladder
Ureteral openings are slits to prevent backflow of urine when bladder contracts
Every 30 seconds peristaltic contraction begins at renal pelvis and moves along ureter, forcing urine toward urinary bladder
Different pathways in males and females:
Due to variations in nature, size, position of reproductive organs
Males – base lies between rectum and pubic symphysis
Females – base sits inferior to uterus and anterior to vagina

36. Urinary Tract Urinary bladder:
Hollow muscular organ/sac for temporary storage of urine; urine flows in until bladder distended and pressure closes urethral openings
Can contain approximately 1 L (stretch receptors triggered at approx 200 mL)
Held in place by umbilical ligaments
Internal surface:
Covered by transitional epithelium (“modified” columnar epithelium)
Has has rugae (folds) that disappear as bladder fills
Trigone
Triangular base (area bounded by ureteral openings and entrance of urethra)
Funnels urine into urethra as bladder contracts
Neck (surrounds urethral opening)
Contains internal urethral sphincter = smooth muscle  involuntary control over discharge of urine from bladder
Smooth muscle layers of bladder wall form detrusor muscle – contraction compresses urinary bladder and expels contents into urethra

37. Urinary Tract Urethra: Female urethra:
Extends from neck of urinary bladder to exterior of body
Drains urine from bladder to exterior opening of body (external urethral meatus/orifice)
Females and males differ in length and function
Female urethra:
Very short (1-2 in. long)
From bladder to vestibule
External urethral orifice/meatus = opening to outside between vagina and clitoris

38. Urinary Tract Male urethra:
Extends from neck of bladder to tip of penis (6-8 in. long)
3 sections:
Prostatic urethra - passes through prostate gland
Membranous urethra
Penetrates urogenital diaphragm (floor of pelvic cavity)
Surrounded by external urethral sphincter (in males and females)
= band of skeletal muscle
Acts as a valve - at rest, contracted; must be voluntarily relaxed to urinate
Penile (spongy) urethra – passes through penis:
From urogenital diaphragm
To external urethral orifice/meatus (opening to outside)

39. Figure 26-18