A&P Exam 4

Major Structures of Urinary System 

• Kidneys

• Ureters

• Urinary bladder

• Urethra 

Kidney functions

• Excretion of wastes

• Regulation of blood ionic composition 

• Regulation of blood pH

• Regulation of blood volume (and blood pressure)

• Maintenance of blood osmolarity 

• Production of hormones 

• Regulation of blood glucose level 

Excretion of wastes

Most wastes result from metabolic reactions

• Include: Urea, ammonia, creatinine, uric acid, and urobilin  (nitrogenous wastes)

Regulation of blood ionic composition 

Kidneys can adjust the amount of ions that are excreted into the urine 

Regulation of blood pH

Kidneys can adjust the amount of acids or bases that are excreted into the urine

Regulation of blood volume (and blood pressure)

• Kidneys can adjust the amount of water that is excreted into the urine  

  • Increased water in blood = increased blood volume = increased blood pressure 

  • Decreases blood volume = decreased blood pressure

Maintenance of blood osmolarity 

Adjusting the amount of water and solutes that are excreted into the urine

Production of hormones 

• Calcitrol

• Eyrthropoetin 

Calcitrol

• Active form of Vitamin D  

• Helps regulate calcium homeostasis 

Eyrthropoetin 

Stimulates the production of blood cells 

Regulation of blood glucose level 

Kidneys can use the amino acid glutamine to synthesize new glucose molecules (gluconeogenesis) to help maintain a normal blood glucose level 

Ureter function

Urine passes through this  

Urinary bladder function

Where urine is stored 

Urethra function

Urine leaves through this

External gross anatomical features of the kidney

• Renal hilum 

• Layers of tissue surrounding each kidney (superficial to deep) 

Renal hilum 

• Indentation on the medial border 

• Passage of blood vessels, nerves, lymphatic vessels, and the ureter 

Layers of tissue surrounding each kidney (superficial to deep) 

• Renal fascia 

• Adipose capsule 

• Renal capsule

Renal fascia 

• Thin layer of dense irregular connective tissue that anchors the kidney to the surrounding structures and to the abdominal wall

Adipose capsule 

Mass of fatty tissue that protects the kidneys and holds it in place within the abdominal cavity  

Renal capsule 

• Smooth, transparent sheet of dense irregular connective tissue that protects and helps maintain the shape of the kidney 

• This layer is continuous with the outer coat of the ureter 

Internal gross anatomical features of the kidney

Regions

Regions

• Renal cortex 

• Renal medulla 

Renal cortex 

• Outer 

• Contains nephrons (functional units) 

Renal medulla 

• Inner 

• Made up of renal pyramids and columns

  • Minor calyx 

  • Major calyx 

  • Renal pelvis 

Columns

Portions of cortex that extend between each pyramid 

Renal papilla 

Apex of each pyramid 

Minor calyx 

Where renal papilla empties urine

Major calyx 

Minor calyx widens to form this 

Renal pelvis 

• Major calyces merge to form this  

• Funnel-shaped expansion at the proximal end of the ureter 

Nephron Parts

 

• Renal corpuscle

• Renal tubule  

Renal corpuscle parts  

• Glomerulus 

• Glomerular (Bowman’s capsule) 

Glomerulus 

Tangled, ball-shaped network of capillaries formed by branches of the renal artery 

Glomerular (Bowman’s capsule) 

• Double-walled epithelial cup that surrounds the glomerular capillaries (visceral and parietal layers) 

• Blood plasma is filtered out of the glomerular capillaries and collected by this

Renal tubule 

• Filtered liquid (filtrate) passes into this 

• Tubules modify filtrate to produce urine

• Collecting duct 

• Papillary ducts 

Renal tubule sections

• Proximal convoluted tubule (PCT) 

• Nephron loop (loop of Henle) 

• Distal convoluted tubule

Collecting duct 

Distal convoluted tubules of several nephrons empty into a single one of these 

Papillary ducts 

• Drain into the minor calyces 

• Several collecting ducts merge to form this 

Functions performed by nephrons and collecting ducts 

• Glomerular filtration

• Tubular reabsorption  

• Tubular secretion

Glomerular filtration

• Movement of water and solutes from plasma into the glomerular capsule -> then into the renal tubule 

• In the glomerulus  

Tubular reabsorption 

• Movement of water and solutes out of the various segments of the tubule and into the peritubular capillaries 

• All along the renal tubules and collecting duct

Tubular secretion

• Movement of water and solutes out of the peritubular capillaries into the tubule for excretion

• Removes a substance from the blood 

• All along the renal tubule and collecting duct   

Filtration membrane

• Leaky barrier 

• Substances from the blood cross three barriers

Substances from the blood cross three barriers

• Glomerular endothelium

• Basement membrane

• Filtration slits

Glomerular endothelium

Prevents filtration of blood cells but allows all components of blood plasma to pass through  

Basement membrane

Prevents filtration of larger proteins 

Filtration slits

Prevents filtration of medium-sized proteins 

Leaky barrier

• Formed by 

  • Glomerular capillaries

  • Podocytes

Podocytes

• Cells that form the visceral layer of the glomerular capsule

• Foot-like processes that wrap around the capillaries but do not fully encapsulate them 

• Form the filtration slits

Glomerular filtration depends on 3 main pressures

• Glomerular blood hydrostatic pressure (GBHP)

• Capsular hydrostatic pressure (CHP) 

• Blood colloid osmotic pressure (BCOP) 

Glomerular blood hydrostatic pressure (GBHP)

• Blood pressure in the glomerular capillaries  

• Created by the imbalance of the afferent and efferent arterioles

Afferent arteriole 

• Larger diameter 

  • Allows more blood to flow into the glomerulus 

Efferent arterioles 

• Small diameter 

  • Prevents blood from leaving

Created by the imbalance of the afferent and efferent arterioles

• Creates a small "back up” of blood - forcing water and solutes through the vessels and into the capsule 

• Promotes filtration by forcing water and solutes through the filtration membrane

Capsular hydrostatic pressure (CHP) 

• Pressure exerted against the glomerulus by the fluid already in the capsular space 

• Opposes filtration 

Blood colloid osmotic pressure (BCOP) 

• Due to presence of proteins in the blood plasma 

• Opposes filtration 

Orange Arrow

Glomerular filtration

Blue Arrow

Tubular reabsorption

Yellow Arrow

Tubular Secretion

Proximal Convoluted Tubule Reabsorption

• Largest amount of solute and water absorption takes place here   

  • 65% of the filtered water, Na+, K+, and Ca²⁺

  • 100% of most filtered organic solutes (glucose and amino acids) 

  • 50% of the filtered Cl-

  • 80% of the filtered HCO₃- 

  • 50% of the filtered urea 

  • Variable amount of Mg²⁺ and HPo₄^2- (phosphate) 

Nephron Loop Reabsorption

• 15% of the filtered water (descending limb) 

• 25% of the filtered Na+, K+, Ca²⁺ 

• 35% of the filtered Cl- 

• 10% of the filtered HCO₃-

• Variable amount of Mg²⁺

DCT Reabsorption

• 5% of the filtered Na+ and Cl- 

• Variable amounts of Ca²⁺ 

Proximal Convoluted Tubule Secretion

• Variable amounts of 

  • H+

  • NH₄+ (ammonium ions) 

  • Urea 

DCT Secretion

Excess K+ can be secreted into the tubular fluid from the bloodstream based on need 

Urinalysis

An analysis of the volume and physical, chemical, and microscopic properties of urine 

Urinalysis Importance

• Reveals much about the state of the  body 

  • Fluid intake

  • Blood pressure

  • Blood osmolarity 

  • Diet 

  • Body temperature 

  • Diuretics 

  • Mental state 

  • General health influence urine volume

Ureter Physiology

• Carry urine from the kidneys to the urinary bladder through peristaltic contractions, hydrostatic pressure, and gravity 

Urinary Bladder Anatomy

Hollow, muscular

Urinary Bladder Layers

• Inner

• Intermediate

• Superficial 

Inner

• Mucosa 

• Mucous membrane made up of traditional epithelium 

Intermediate

• Muscular layer, also called the detrusor muscle 

• Consists of 3 layers of smooth muscle 

• Internal urethra sphincter 

• External urethral sphincter 

Internal urethra sphincter 

Formed by circular muscle fibers around the opening to the urethra 

External urethral sphincter 

• Skeletal muscle

• Inferior to internal urethral sphincter  

Superficial

• Posterior and inferior surfaces = adventitia

• Superior surface = serosa

Adventitia

Layer of areolar connective tissue

Serosa

Layer of peritoneum

Urinary bladder physiology

Where urine is stored 

Urethra anatomy

Small tube leading from the internal urethral orifice of the urinary bladder to the exterior of the body 

Urethra in males

• It passes through the prostate, then through the deep perineal muscles, and finally through the penis

  • Prostatic urethra 

  • Membranous urethra 

  • Spongy urethra

Urethra physiology

Conveys urine to the outside 

Primary functions of the reproductive systems

• Produce gametes 

• Transport gametes

• Enable fertilization 

• Support development (female)

• Secrete hormones 

Gametes

Sex cells

Male Gametes

• Sperm 

  • Small

  • Motile 

Female Gametes

• Oocyle (egg) 

  • Large 

  • Non-motile 

Role of hormones in regulating reproduction

• Regulate reproductive processes

• Control gamete production 

• Maintain secondary sex characteristics 

Scrotum structure

• External pouch 

• Dartos muscle 

• Cremaster muscle 

Dartos muscle function

Wrinkles skin (heat conservation) 

Cremaster muscle function  

Raises/lower testes 

Scrotum functions

• Houses testes 

• Keeps testes 2-3 degrees C below body temperature 

• Essential for normal sperm production 

Testes Structure

• Male gonads located in scrotum 

• Seminiferous tubules 

• Sertoli (sustentacular) cells 

• Leydig (interstitial) cells

Seminiferous tubules 

Site of spermatogenesis 

Sertoli (sustentacular) cells 

• Support developing sperm 

• From blood-testis barrier

• Produces inhibin

Leydig (interstitial) cells

Produce testosterone

Testes Function

• Produce

  • Sperm

  • Testosterone 

Pathway of sperm from production to exit

• Seminiferous tubules 

• Epididymus 

• Ductus (vas) deferens 

• Ejaculatory duct

• Urethra

Epididymus function

• Site of 

  • Sperm maturation

  • Storage

Ductus (vas) deferens function

Carries sperm from epididymis 

Urethra function

Shared exit pathway 

Accessory glands 

• Forms semen 

• Seminal vesicles 

• Prostate gland 

• Bulbourethral glands 

Seminal vesicles 

Add fructose-rich fluid (~60%)

Prostate gland 

Adds enzymes (~25%)