Survey of Anatomy & Physiology Chapter 16

Part One: The Urinary System: Filtration and Fluid Balance

16

Urinary system acts as purification plant, cleaning blood of waste materials

Liver does some purification, but urinary system controls electrolyte and fluid balances for body

IntroductionIntroduction

Kidneys filter blood, reabsorb and secrete ions, and produce urine

Without this important function you would die in a few days

IntroductionIntroduction

Urinary system consists of two kidneys, bean-shaped organs located in superior dorsal abdominal cavity that filter blood and make urine, as well as accessory structures

System OverviewSystem Overview

Ureter is tube that carries urine from each kidney to single urinary bladder, located in inferior ventral pelvic cavity

Urinary bladder is basically expandable sac that holds urine


Job of urinary system is to make urine, thus controlling body's fluid and electrolyte balance and eliminating waste products


http://www.youtube.com/watch?v=lfGYd1wrTgE



3 Processes to Make Urine3 Processes to Make Urine

Filtration involves passing substances in blood through walls of glomerular capillaries that are dotted with pores to create filtrate; contains various substances that can either be

Function of the Urinary SystemFunction of the Urinary System

Reabsorbed from tubules to capillaries or

Secreted from capillaries to tubules and removed in the urine

Part of filtrate is reabsorbed and sent back into bloodstream, some is secreted into tubules and eliminated from body

Function of the Urinary SystemFunction of the Urinary System

Figure 16-1Figure 16-1Anatomy of the urinary Anatomy of the urinary

system.system.

Kidney covered by fibrous layer of connective tissue called renal capsule

Indentation that gives kidney bean-shaped called renal hilum

External External Anatomy of Anatomy of the Kidneythe Kidney

Anatomy of the urinary system

At hilum, renal arteries bring blood to kidneys to be filtered; blood leaves kidney via renal vein

Ureter also attached to transport urine from kidney to bladder

External External Anatomy of Anatomy of the Kidneythe Kidney

Anatomy of the urinary systemAnatomy of the urinary system

Renal cortex: outer layer, grainy in appearance; little obvious structure to naked eye; where blood filtration occurs

Internal Internal Anatomy of Anatomy of the Kidneythe Kidney


◦Renal medulla: Contains number of triangle-shaped, striped areas called renal pyramids



◦Renal medulla:

◦Renal pyramids composed of collecting tubules for urine formed in kidney



Renal pelvis Funnel, divided into two or three large collecting tubes called major calyces



Renal pelvis Each calyx divided into several minor calyces, forming cup-shaped areas around tips of pyramids to collect urine that continually drains through pyramids



Filtration and Collection SystemFiltration and Collection System

Figure 16-2The internal and external

anatomy of the kidney

Figure 16-3Renal blood vessels and the pathway of blood

through the renal system.

Consisting of millions of microscopic funnels and tubules

Divided into two distinct parts:Renal corpuscleRenal tubule

The Nephron-The Nephron-Functional Unit of KidneyFunctional Unit of Kidney

Blood flows through afferent arteriole and into the glomerulus, a capillary ball

Walls of glomerular capillaries dotted with pores


Surrounding glomerulus is a double-layered membrane called glomerular capsule (Bowman's capsule)


Blood flows into glomerulus and blood cells and few large molecules, mainly plasma protein, remain in blood.

Water and small solutes allowed to pass through pores in capillaries across filter and into glomerular capsule

The Nephron-The Nephron-FiltrationFiltration


http://www.youtube.com/watch?v=Hlg7oh2OcOc

http://www.youtube.com/watch?v=Hlg7oh2OcOc

Blood then exits the glomerulus through the efferent arteriole and the small blood vessels become part of the peritubular capillaries that surround the renal tubules


Material filtered from blood into glomerular capsule is called the glomerular filtrate

If blood or protein leaks into urine, this can indicate kidney filtration problem

The Nephron-The Nephron-FiltrationFiltration


The rest of nephron is series of tubes known as renal tubules

Glomerular filtrate travels from glomerular capsule into first part of renal tubule called the proximal tubule

Wall of proximal tubule made cells with microvilli

The NephronThe Nephron


From proximal tubule, glomerular filtrate flows into nephron loop (Loop of Henle)

Nephron loop consists of:

Descending loop (similar in structure to proximal tubule) and Ascending loop

The NephronThe Nephron


http://www.youtube.com/watch?v=_CnhwhHsWLI&list=PL315D7CADE5B89492



Glomerular filtrate then flows into distal tubule

From distal tubule, glomerular filtrate flows into one of several collecting ducts,


Collecting ducts lead to

1) minor calyces, then to

2)major calyces, 3)renal pelvis, 4) ureterAt this point,

glomerular filtrate is urine

Flow of Urine to Flow of Urine to External KidneyExternal Kidney

Figure 16-5Figure 16-5A functional renal A functional renal

unit.unit.

Kidney controls fluid and electrolyte balance by controlling urine volume and composition

In order to form urine, nephron must perform three processes:

Urine Formation-3 ProcessesUrine Formation-3 Processes

Urine Formation at the Urine Formation at the Level of the NephronLevel of the Nephron

Urine Urine FormationFormation

Urine Formation at the Level Urine Formation at the Level of the Nephronof the Nephron

Filtration moves fluid and chemicals into nephron from blood

Reabsorption and secretion control concentration of chemicals and volume of urine

Urine Urine Formation-Formation-SummarySummary

Urine Formation at the Urine Formation at the Level of the NephronLevel of the Nephron

Due to the action of reabsorption and secretion, the urine is chemically very different that the original glomerular filtrate.

In other words, what starts out looking very similar to blood, changes after passing through the tubules

Urine Urine Formation-Formation-SummarySummary

Urine Formation at the Level Urine Formation at the Level of the Nephronof the Nephron

Figure 16-7Figure 16-7The processes involved The processes involved

in urine formationin urine formation

Figure 16-8Figure 16-8Filter selectivityFilter selectivity

Control of filtration (amount and composition of fluid filtered) is determined by size of pores in the walls of the renal corpuscle

Like a coffee filter, it is selective as to what it let’s pass through

Only when filter is damaged, do blood and protein pass through

Only when filter is damaged, do blood and protein pass through

If GFR controls rate of urine formation then….

Tubular reabsorption and secretion control chemistry and volume of urine

Control of Control of Tubular Tubular

Reabsorption Reabsorption and Secretionand Secretion

REMEMBER:Substances that are reabsorbed move from tubule back to bloodstream via peritubular capillaries and stay in body

Substances that are secreted stay in tubule and eventually leave body via urine



IMPORTANT:Anything that affects reabsorption and secretion affects urine chemistry and/or composition and volume

Control of Tubular Control of Tubular Reabsorption and Reabsorption and

SecretionSecretion

First thing that affects tubular reabsorption and secretion is tubule permeability

Each portion of tubule can reabsorb and secrete different substances



Molecules move across membranes through several different methods (diffusion, osmosis, active or passive transport)

Control of Tubular Control of Tubular Reabsorption and Reabsorption and

SecretionSecretion

Differences in tubular permeability result in dramatic differences in which molecules are reabsorbed or secreted in each part of tubule

Control of Tubular Reabsorption Control of Tubular Reabsorption and Secretionand Secretion

Table 16-2 Table 16-2 Individual Tubule Individual Tubule

FunctionsFunctions

Most of important substances reabsorbed or secreted in PROXIMAL TUBULE

90% of water reabsorbed in descending loop

Most of important substances reabsorbed or secreted in PROXIMAL TUBULE

90% of water reabsorbed in descending loop

Filtrate flows into descending loop, reabsorbing water and increasing concentration of ions

Balancing Balancing H20 & IONSH20 & IONS

As filtrate enters ascending loop, fluid is concentrated because of water loss, membrane is permeable to only ions, so ions are reabsorbed from ascending loop

Balancing H20 Balancing H20 & IONS& IONS

Figure 16-11Figure 16-11Sites of tubular reabsorption and Sites of tubular reabsorption and

secretionsecretion

Figure 16-11Figure 16-11Sites of tubular Sites of tubular

reabsorption and reabsorption and secretionsecretion

Use handout and follow along

Use handout and follow along

Complete worksheets using your notes from Power Point Presentation notes and textbook on •The Nephron (page 457 and slides 22-30) •Glomerular Filtration (page 458 and PPP)

Complete worksheets using your notes from Power Point Presentation notes and textbook on •The Nephron (page 457 and slides 22-30) •Glomerular Filtration (page 458 and PPP)

Part Two:The Urinary System: Filtration and Fluid Balance

16

Higher pressure in glomerulus increases filtration, while lower pressure decreases filtration

Glomerulus protected from minor changes in blood pressure by mechanism called autoregulation

Filtration Filtration Rate-Rate-

Amount of Amount of Filtered FluidFiltered Fluid

Pressure Affects Pressure Affects Glomerular FiltrationGlomerular Filtration

As systemic BP increases, afferent arterioles leading into glomerulus constrict, thereby decreasing amount of blood getting into glomerulus

Autoregulation Autoregulation of GFR*of GFR*

*glomerular filtration rate

BP and Formation of BP and Formation of Urine-GFR*Urine-GFR*

Autoregulation can be overridden when BP must be regulated.

Kidney controls fluid volume, so when BP or blood volume drops, (extreme blood loss) GFR decreases to conserve fluid volume

Autoregulation Autoregulation of GFRof GFR

BP and Formation of Urine-BP and Formation of Urine-Glomerular FiltrationGlomerular Filtration

Glomerular filtration rate can decrease to conserve fluid when blood pressure falls, or increase filtration if blood pressure rises

Autoregulation Autoregulation of GFRof GFR

BP and Formation of Urine-BP and Formation of Urine-Glomerular FiltrationGlomerular Filtration

ADH is a hormone that regulates blood pressureMade by hypothalamus and secreted from posterior pituitary when BP decreases or ionic concentration increases

ADH-Hormone that controls ADH-Hormone that controls Reabsorption and SecretionReabsorption and Secretion

Increases permeability of distal tubule and collecting duct; more water reabsorbed, increasing blood volume and blood pressure, and diluting ionic concentration

ADH-Hormone that controls ADH-Hormone that controls Reabsorption and SecretionReabsorption and Secretion

Less urine is producedAlcohol inhibits ADH production, increasing urine production

ADH-Hormone that ADH-Hormone that controls Reabsorption controls Reabsorption

and Secretionand Secretion

The Urinary Bladder –The Urinary Bladder –Next Stop for the UrineNext Stop for the Urine

Urinary bladder: small, hollow organLined with transitional epithelium, which is the only epithelium stretchy enough to expand as bladder fills

The Urinary Bladder The Urinary Bladder and Urination Reflexand Urination Reflex

Ability to stretch enhanced by series of pleats called rugae

Has muscular wall consisting of circular and longitudinal smooth muscle

Muscle layer known as detrusor muscle

The Urinary Bladder The Urinary Bladder and Urination Reflexand Urination Reflex

Figure 16-14Figure 16-14The urinary The urinary

bladder.bladder.

Figure 16-15Figure 16-15Control of Control of urinationurination

As urine accumulates, bladder fills and stretchesStretch triggers urinary reflex and need to void to empty bladder

Figure 16-15Figure 16-15Control of urinationControl of urination

Urination had been thought to be spinal reflex; new research

indicates controlled by brain

Urination had been thought to be spinal reflex; new research

indicates controlled by brain

When bladder is full, signals sent from bladder to spinal cord to pons, thenPons sends parasympathetic signals down spinal cord, causing contraction of muscular walls of bladder, and bladder empties

Figure 16-15Control of urination

Urine leaves bladder via urethra, thin muscular tube lined with several different types of epithelium along its length


Parts of brain can inhibit urination by controlling internal urethral sphincter, valve at junction of bladder and urethra, and external urethral sphincter, valve that is part of muscles of pelvic floor


Sympathetic stimulation of these sphincters prevents urine from leaving bodyAlthough you have little control over contractions of bladder wall, you have very good voluntary control over sphincters

Survey of Anatomy & Physiology Chapter 16

Health & Medicine

balancing h20

glomerular filtrate flows

important substances reabsorbed

kidney blood flows

glomerular filtrate

blood pressure

urinary system

controls reabsorption