Ch27 Urinary System

7/31/2019 Ch27 Urinary System

1/52

27-1

Human Anatomy, First EditionMcKinley & O'Loughlin

Chapter 27 :

UrinarySystem


2/52

27-2

General Structure and Functions

of the Urinary System General Concept:

Waste products accumulate in blood

Are toxic Must be removed to maintain

homeostasis

Urinary System organs remove waste products from the blood

then from the body

Major homeostatic system


3/52

27-3

General Structure and Functions

of the Urinary System Organs of the Urinary System:

Kidneys

Ureters

Urinary Bladder

Urethra

Primary organs: kidneys filter waste products from the bloodstream

convert the filtrate into urine.

The Urinary Tract: Includes:

ureters

urinary bladder

urethra

Because they transport the urine out of the body.


4/52

4


5/52

5


6/52

6


7/5227-7

Functions of the Urinary System Removing waste products from the bloodstream.

Storage of urine.

the urinary bladder is an expandable, muscular sac that can

store as much as 1 liter of urine Excretion of urine.

Blood volume regulation.

the kidneys control the volume of interstitial fluid and bloodunder the direction of certain hormones

Regulation of erythrocyte production. as the kidneys filter the blood, they are also indirectly

measuring the oxygen level in the blood

Erythropoietin (EPO): hormone produced by kidney Released if blood oxygen levels fall

Stimulates RBC production in red bone marrow


8/5227-8

Kidneys: Gross and Sectional

Anatomy Retroperitoneal

Anterior surface covered with peritoneum

Posterior surface against posteriorabdominal wall

Superior pole: T-12

Inferior pole: L-3 Right kidney ~ 2cm lower than left

Adrenal gland on superior pole


9/52

9


10/5227-10


Anatomy Hilum: concave medial border

Renal sinus: internal space

Houses blood vessels, lymphatic vessels,nerves

Houses renal pelvis, renal calyces

Also fat


11/5227-11


Anatomy Surrounding tissues, from deep to superficial:

Fibrous capsule (renal capsule) Dense irregular CT

Covers outer surface

Perinephric fat (adipose capsule) Also called perirenal fat

Completely surrounds kidney

Cushioning and insulation

Renal fascia Dense irregular CT

Anchors kidney to posterior wall and peritoneum

Paranephric fat Between renal fascia and peritoneum


12/52

12


13/5227-13


Anatomy Sectioned on a coronal plane:

Renal Cortex Renal arches Renal columns

Renal Medulla Divided into renal pyramids

8 to 15 per kidney Base against cortex

Apex called renal papilla


14/52

27-14


Anatomy Minor calyx:

Funnel shaped Receives renal papilla 8 to 15 per kidney, one per pyramid

Major calyx Fusion of minor calyces 2 to 3 per kidney

Major calyces merge to form renal pelvis Renal Lobe

Pyramid plus some cortical tissue 8 to 15 per kidney


15/52

15


16/52

16


17/52

27-17

Blood Supply to the KidneyAbout 20 to 25% of cardiac output to

kidneys

Path: Renal artery to segmental arteries to

interlobar arteries to arcuate arteries tointerlobular arteries to:

Afferent arteriole to glomerulus to efferentarteriole to peritubular capilaries and vasarecta


18/52

18


19/52

27-19

Blood Supply to the Kidney Blood plasma is filtered across the glomerulus

into the glomerular space.

Once the blood plasma is filtered blood leaves the glomerulus

enters an efferent arteriole.

efferent arteriole is still carrying oxygenatedblood

a gas and nutrient exchange with the kidneytissues has not yet occurred.


20/52


21/52

27-21

Blood Supply to the Kidney Path for veins:

Interlobar veins to arcuate veins to

interlobar veins to the renal vein


22/52

22


23/52

27-23

Nephrons The functional filtration unit in the kidney. Consists of the following:

Renal corpuscle

Glomerulus Glomerular capsule (Bowmans capsule)

Proximal convoluted tubule (PCT) Nephron loop (loop of Henle)

Ascending loop of Henle Descending loop of Henle

Distal convoluted tubule (DCT) collectively called the renal tubule

In both kidneys: approximately 2.5 million nephrons. Are microscopic: measure about 5 centimeters in

length.


24/52

27-24

Nephrons Cortical Nephrons

Near peripheral edge of cortex

Short nephron loops Have peritubular capillaries

Juxtamedullary nephrons

Near corticomedullary border Long nephron loops

Have vasa recta


25/52

25


26/52

27-26

Urine Formation Three processes

Filtration

Renal corpuscle: forms filtrate From blood to tubule

Reabsorption Mostly PCT

Water and salt: rest of nephron From tubule to blood

Secretion From blood to tubule


27/52

27-27

Renal Corpuscle Vascular pole

Afferent and efferent arterioles

Tubular pole Connects to PCT

Two structures: Glomerulus and glomerular capsule

Glomerulus Capillary bed

High pressure

fenestrations


28/52

27-28

Renal Corpuscle Glomerular Capsule

Parietal layer Simple squamous epithelium

Visceral layer Podocytes

Pedicels

Filtration slits

Capsular space (Bowmans capsule): location offiltrate

Filtration membrane Fenestrations

Filtration slits


29/52

29


30/52

30


31/52

27-31

Proximal Convoluted Tubule Begins at tubular pole of the renal corpuscle. Cells: simple cuboidal epithelium

actively reabsorb from the filtrate: almost all nutrients (glucose and amino acids) electrolytes plasma proteins

Osmosis: reabsorption of 60% to 65% of thewater in filtrate.

Have microvilli

Solutes and water: moved into blood plasma

via the peritubular capillaries.


32/52

27-32

Nephron Loop (loop of Henle) originates at end of proximal convoluted tubule

projects toward and/or into the medulla.

Each loop has two limbs. descending limb:

from cortex toward and/or into the medulla

ascending limb:

returns back to the renal cortex


33/52

33


34/52

34


35/52

27-35

Distal Convoluted Tubule begins at the end of the thick ascending limb of the

nephron loop adjacent to the afferent arteriole (important physiologically)

Juxtaglomerular apparatus.

primary function: Secretion From blood plasma to filtrate. secretes ions

potassium (K+) acid (H+)

Reabsorption of water also occurs: influenced by two hormones

Aldosterone antidiuretic hormone (ADH).


36/52

27-36

Collecting Collecting Ducts Function in a well hydrated person:

transport the tubular fluid into the papillary duct and theninto the minor calyx.

Function in a dehydrated person: water conservation

more-concentrated urine is produced.

ADH can act on the collecting duct epithelium Cells become permeable to water

Water moves from filtrate into blood plasma

Involves vasa recta.


37/52

27-37

Innervation of the Kidney innervated by a mass of autonomic nervous system

fibers

called the renal plexus.

The renal plexus

accompanies each renal artery

enters the kidney through the hilum.


38/52

27-38

Urinary Tract : Ureters long, fibromuscular tubes

conduct urine from the kidneys to the urinarybladder.

average 25 centimeters in length retroperitoneal.

ureters originate at the renal pelvis

extend inferiorly to enter the posterolateral wall of

the base of the urinary bladder. wall is composed of three concentric tunics.

mucosa

muscularis

adventitia.


39/52

27-39

Urinary Tract Urinary Bladder The urinary bladder:

expandable, muscular container serves as a reservoir for urine

positioned immediately superior and posterior to the pubic

symphysis. in females

the urinary bladder is in contact with the uterus posterosuperiorlyand with the vagina posteroinferiorly.

in males it is in contact with the rectum posterosuperiorly and is

immediately superior to the prostate gland.

is a retroperitoneal organ. when empty exhibits an upside-down pyramidal shape. Filling with urine distends it superiorly until it assumes an oval

shape.


40/52

27-40

Urinary Tract Urinary Bladder Trigone

posteroinferior triangular area of the urinary bladder wall formed by imaginary lines

connect the two posterior ureteral openings

and the anterior urethral opening. The trigone remains immovable as the urinary

bladder fills and evacuates. It functions as a funnel

directs urine into the urethra as the bladder wall contracts

four tunics mucosa submucosa Muscularis: called the detrusor muscle adventitia.

Internal urethral sphincter (smooth muscle)


41/52

41


42/52

42


43/52

43


44/52

27-44

Micturition (Urination) The expulsion of urine from the bladder.

Initiated by a complex sequence of events called themicturition reflex.

The bladder is supplied by both parasympathetic andsympathetic nerve fibers of the autonomic nervous

system.


45/52

27-45

Urethra Fibromuscular tube

exits the urinary bladder through the urethral opening at anteroinferior surface

conducts urine to the exterior of the body. Tunica mucosa: is a protective mucous membrane

houses clusters of mucin-producing cells called urethralglands.

Tunica muscularis: primarily smooth muscle fibers help propel urine to the outside of the body.

Two urethral sphincters: Internal urethral sphincter

restrict the release of urine until the pressure within the urinarybladder is high enough

External urethral sphincter

and voluntary activities needed to release the urine areactivated.


46/52

27-46

Urethra The internal urethral sphincter

involuntary (smooth muscle) superior sphincter surrounding the neck of the bladder,

where the urethra originates. a circular thickening of the detrusor muscle controlled by the autonomic nervous system

The external urethral sphincter inferior to the internal urethral sphincter formed by skeletal muscle fibers of the urogenital

diaphragm. a voluntary sphincter controlled by the somatic nervous system this is the muscle children learn to control when they

become toilet-trained


47/52

27-47

Female Urethra Has a single function:

to transport urine from the urinary bladder to the vestibule,an external space immediately internal to the labia minora

3 to 5 centimeters long, and opens to the outside ofthe body at the external urethral orifice located in thefemale perineum.


48/52

48


49/52

27-49

Male Urethra Urinary and reproductive functions:

passageway for both urine and semen

Approximately 18 to 20 centimeters long.

Partitioned into three segments: prostatic urethra is approximately 3 to 4 centimeters long and is the

most dilatable portion of the urethra

extends through the prostate gland, immediately inferior to the malebladder, where multiple small prostatic ducts enter it

membranous urethra is the shortest and least dilatable portion

extends from the inferior surface of the prostate gland through the

urogenital diaphragm spongy urethra is the longest part (15 centimeters)

encased within a cylinder of erectile tissue in the penis called thecorpus spongiosum

extends to the external urethral orifice


50/52


51/52

27-51

Aging and the Urinary System Changes in the size and functioning of the kidneys begin at 30. Gradual reduction in kidney size. Reduced blood flow to the kidneys. Decrease in the number of functional nephrons. Reabsorption and secretion are reduced. Diminished ability to filter and cleanse the blood. Less aldosterone or antidiuretic hormone. Ability to control blood volume and blood pressure is reduced.

Bladder decreases in size.

More frequent urination. Control of the urethral sphinctersand micturitionmay be lost.


52/52

52

Documents

Ch27 Urinary System