Biology 30S

The Excretory System

Identify the primary metabolic wastes produced in the human body and the source of each.

Describe the roles of the major excretory structures in eliminating wastes and helping the body maintain homeostasis.

Describe the important role of the liver in the process of excretion and the maintenance of homeostasis.

Identify structures of the human urinary system from a diagram, model, or specimen, and describe the function of each.

Explain the processes of filtration, reabsorption, and secretion in the nephron.

Describe the feedback mechanisms associated with water and salt balance and their role in the maintenance of homeostasis in the human body.

Describe what types of information can be gained through urinalysis.

Investigate and describe issues related to kidney failure and treatment options available.

The Excretory System

Read the following paragraphs, and answer the questions below:

1. In your own words, explain why the excretory system is important to your body?

2. Why is it dangerous to be unable to sweat?

3. What substance does the liver change into urea?

4. Which organs turn liquid into urine?

5. What happens if waste builds up in our body?

Introduction to the Excretory System

Each body activity uses _________________ and generates ___________________. If waste products were not removed, they would quickly accumulate in harmful

proportions. Some wastes are _______________________ and pose a serious threat to health if

they are not removed promptly. The process of getting rid of metabolic wastes is called _______________________. The chemical composition of intercellular fluid is for the life of the cells. If it becomes too salty, the cells can become dehydrated. If it gets too watery the cells can bloat.

Remember this back from Unit One?....

Excretion and Homeostasis

Excretion aids homeostasis by removing wastes and regulating the salt and water balance.

The blood picks up _____________________________________________________ that may be present and carries them to the excretory organs, which channel the wastes out of the body.

Fortunately, atoms and molecules do not wear out, but may be changed or rearranged and used over and over again.

Many of the end products of various cell activities can be ______________________ and used in other processes.

As a result, the amount of waste that actually needs to be discharged from the body is very small in relation to the amount of work done by all the cells of the human body.

Several organs take part in human excretion. The skin, lungs, liver, and the transport system play important roles; however, the main excretory organs are the kidneys.

Organs associated with the Excretory System:

a) The Skin

The skin is the _____________________________________ of the body. The skin covers an area of _________________________________ on an average adult. The thickness of the skin varies from 0.5 mm on the eyelids to 6 mm on the soles of the

feet There are 2 general layers of the skin: _______________________________________.

Epidermis the __________ layer is called the epidermis and is made up of layers of flat cells the surface of cells of this layer are __________ they are constantly rubbing and being replaced by the cells below them this outer layer of skin provides a ______________________shield against germs

and bacteria

Dermis this layer is under the epidermis the cells in this layer are still ________________ this layer contains blood vessels, nerve endings, sweat and oil glands, hair

follicles, and fat cells the sweat glands have tubes that lead to the surface of the skin at points called

sweat pores ___________________________ is released at these sweat pores

b) The Lungs

Gas exchange occurs between the microscopic capillaries and the _________________ in the lungs

Oxygen is diffused into the blood stream from the alveoli into the __________________ Oxygen is attracted to, and held by, the hemoglobin in the red blood cells of the body Oxygen is released into living cells and used in cellular respiration- the releasing of

energy from food and oxygen within the individual cells The waste product from cellular respiration is ______________________________

which is diffused out of the cell and carried back to the lungs and diffused from the capillaries into the alveoli and ________________________ by the lungs

____________________________________ is also exhaled during this process

c) The Liver

the liver is located just to right of the stomach _____________ in the blood is removed in the liver and stored as _________________ when the sugar level in the blood goes down the liver breaks down the glycogen and

releases sugar back into the blood if there is no room for the liver to store glycogen the liver changes the sugar to _______

and stores it in other parts of the body the liver also removes from our bodies ___________________________________, such

as poisons in fish, poisonous fumes from paint, and chemicals sprayed on food the liver also changes the hemoglobin from dead red blood cells into _______________,

which is used in the small intestine to break down fats _____________________ from the large intestine is removed from the body by the liver

d) The Kidneys

The kidneys are the main organs of the _____________________________________ as they are the body’s _____________________________ system

The kidneys help maintain a balance among the elements inside the body (this balance is referred to as homeostasis)

The kidneys perform the following important jobs:o They remove _________________ and other wastes from the bloodo They regulate the amount of _____________________ in the circulatory systemo They ____________________ the amounts of certain substances in the blood

The kidneys filter wastes and poisons from the blood at an incredible rate The entire blood supply of the body passes through the kidneys _____every 30 minutes Within each kidney are an estimated _______________________ microscopic nephrons

where filtering actually takes place Each nephron contains a cluster of capillaries known as a ________________________ A cup shaped sac called a ______________________capsule surrounds each glomerulus The blood that flows through the glomerulus is under great pressure This causes water, urea, glucose and minerals into the Bowman’s capsule Red blood cells, white blood cells, and protein remain in the blood As blood continues through the blood vessels, it winds around the

___________________ -during this time _____________________________ occurs Glucose and chemicals such as potassium, sodium, hydrogen, magnesium, and calcium

are reabsorbed into the blood Almost all of the water removed during filtration returns to the blood during the

reabsorption phase-the water and mineral composition of the body is actually regulated in the kidneys

The kidneys control the amount of ________________ in our bodies

Now, only __________________ are in the nephrons These wastes are called _______________ and include ________________________

__________________________________ There may also be some sugar and nutrients present if there is an excess of these

substances in the blood The cleansed blood goes into the veins that carry the blood from the kidneys and into a

major vein that carries the blood back to the __________________ From the heart, the __________________ blood will circulate throughout the

_______________.Waste Products and the Excretory System

WasteProduct

Originof

Waste Product

ExcretoryOrgan

Ammonia

Urea

Carbon Dioxide

Water

Mineral Salts

Why is excrement (poop) not included in this list of metabolic wastes?

______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Excretion Questions

1. Excretion is the process of ______________________________________________________.

2. If the intercellular fluid becomes too concentrated with salts, sugars, amino acids and other constituents, it becomes _____________________________.

3. If the intercellular fluid is too watery the cell could _________________________________.

4. While the transport system plays an important role in excretion of wastes, the four main organs of excretion are:

a. _________________________b. _________________________c. _________________________d. _________________________

5. Three substances excreted by the lungs are:a. _________________________b. _________________________c. _________________________

6. Sweat consists of:a. _________________________b. _________________________c. _________________________

7. Perspiration, if left on skin may have an odor because? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

8. When the liver breaks down amino acids to form useful pyruvic acid, it also produces harmful __________________________________.

The Kidneys

The kidneys remove _____________________________________ from the body by _______________________________________________.

They work continuously, processing all of the blood in the body every 30 minutes. Every 24 hrs they kidneys filter approximately _____________________ of fluid and

return to the bloodstream all but __________________, which are excreted as urine.

The excretory system consists of:o 2 kidneys: bean-shaped organs lying near the back of the abdominal cavityo 2 ureters: lead from kidney to the urinary bladdero 1 bladder: lies low in the abdominal cavityo 1 urethra: extends from the bladder to the exterior of the body, carrying urine

though the urogenital organs

The kidney, bean-shaped and about _____________________________, has a dark coloured core which is densely packed with _______________________________.

These vessels form a network of capillaries and small tubes known as the ___________. The medulla is divided up into a number of triangular shaped sections called

_________________________________________. Each pyramid consists of _______________________, which branch into smaller and

smaller arterioles, the tiniest of which delivers blood to the______________________. Likewise many tiny ____________________, taking blood away from the nephron join

together making larger and larger venules, finally making up the ___________________. The pyramid also contains a great number of _______________________________

which empty the urine into the central cavity, known as the ______________________.

The Three Basic Renal Processes:

1. ___________________________ – the passage of protein free substances through the capillaries of the glomerulus into the Bowman’s Capsule.

2. __________________________________ – the removal of water and useful solutes from the filtrate

3. __________________________________ – the addition of certain substances to the filtrate

Filtration _____________________ is filtered by nephrons Each nephron begins in a renal corpuscle, composed of a glomerulus enclosed in a

Bowman’s Capsule ____________________, ______________________ and other __________________

are filtered out of the glomerulus by a process of filtration. The filtrate continues on through the proximal tubule all the way through to the

collecting duct to form urine.

Re-absorption Process by which ______________ and _______________ are removed from the

tubular fluid (filtrate) and transported to the blood. Two step process: Begins with the _______________ or _______________ extraction of substances from

the filtrate into the ____________________________ (connective tissue that surrounds the nephrons)

________________________ of these substances from the interstitium into the ______________________

Water and solutes such as Na are reabsorbed

Tubular Secretion The cells of the tubules remove certain molecules and ions from the blood and deposit

these into the fluid within the tubules Tubular secretion of __________ is important in maintaining control of the

____________________________.o When the pH of the blood starts to drop, more hydrogen ions are secretedo If the blood should become too alkaline, secretion of the hydrogen ions is

reducedo In maintaining the pH of the blood within its normal limits of _____________,

the kidney can produce a urine with a _________________________________

The Nephron

1. Renal Capsule – Ultrafiltration

- The renal artery splits into numerous arterioles, each feeding a nephron.- The arteriole splits into numerous capillaries, which form a knot called a

_____________________.- The glomerulus is enclosed by the ________________________________________ the

first part of the nephron.- The arteriole leading into the glomerulus ________________________ is wider than the

one leading out _________________________ so there is a _______________________ in the capillaries of the glomerulus.

- The blood pressure in the capillaries is 60-70 mm Hg, whereas elsewhere in the body capillary pressure is only 25 mm Hg.

- This pressure forces ___________________ out of the blood by ultrafiltration. - Those substances that do pass from the glomerulus into the capsule comprise what is

called the_______________________. - _____________________ and _______________________________ are too big to pass

through the tiny pores in the capsule capillaries. - Substances such as _____________________________________________ are made up

of __________________________ which can pass easily through the _____________________ to enter the capsule.

2. Proximal Convoluted Tubule – Re-absorption- ____________________(14 mm) and __________________ part of the nephron.

- It is lined with epithelial cells containing microvilli and numerous mitochondria.- In this part of the nephron over _________________________________________ into

the tissue fluid and then to the blood. - This ensures that all the ____________________________ that were filtered out of the

blood (such as glucose and amino acids) are now returned to the blood. - All ________________, all __________________, and most _______________________

are reabsorbed by active transport from the filtrate to the tissue fluid. They then diffuse into the blood capillaries.

- 80% of the water is reabsorbed to the blood by osmosis.

3. Loop of Henle – Formation of a Salt Bath- The job of the loop of Henle is to make the tissue fluid in the medulla

____________________compared to the filtrate in the nephron.- The purpose of this _____________________________________________________.- The loop of Henle does this by pumping sodium and chloride ions out of the filtrate into

the tissue fluid.- The first part of the loop (the descending loop) is _______________________________,

but some water leaves by osmosis.- This makes the filtrate more _________________________ as it descends. - The second part of the loop (the ascending loop) contains Na+ and Cl- pumps, so these

ions are actively transported out of the filtrate into the surrounding tissue fluid. - Water would follow by osmosis, but it cannot because the ascending loop is

___________________________________________. - Therefore the _________________________________ (hypertonic) and the

________________________________________________(hypotonic). - Since the filtrate is most concentrated at the base of the loop, the tissue fluid is also

more concentrated at the base of the medulla.

4. Distal Convoluted Tubule – Homeostasis and Secretion- Certain substances are actively transported from the blood into the filtrate, in other

words they are ________________________. - It is relatively short and has a boarder of microvilli with numerous membrane pumps for

active transport.- The important point about this secretion is that it is _____________________________,

so this is the _____________________________ part of the kidney. - Substances secreted include _____ (for pH homeostasis), _____ (for salt homeostasis),

___________________, and other ______________________________.

5. Collecting Duct – Concentration- As the collecting duct passes through the hypertonic salt bath in the medulla, water

leaves the filtrate by osmosis, so concentrating the urine and conserving water. - The water leaves through special _________________________ in the cell membrane

called _________________________. - These aquaporin channels are controlled by a hormone called _________ so allowing

the __________________________________________________________________.

Excretory System Matching Questions

Match each of the descriptions (#1-10) with a the appropriate word (a-n). Write the correct word beside the description.

a) The tube leading from the kidney to the urinary bladder

b) Microscopic filtration units in the kidney

c) The name of the artery carrying blood to the kidney

d) Minute “balls” of capillaries in the nephron

e) The major organ of excretion

f) The tubule carrying filtrate from the Bowman’s capsule to the loop of Henle

g) The tube that carries urine away from the bladder

h) The fluid that passes from the glomerulus to the Bowman’sCapsule

i) A ring of muscles that can close off a tube

j) A waste product, high in nitrogen, that is found in urine

Word Bank:

a. Bowman’s Capsuleb. Glomerulusc. Loop of Henled. Nephrone. Ureterf. Urethrag. Filtrateh. Proximal Tubulei. Distal Tubulej. Ureak. Renal Arteryl. Sphincterm. Urinen. Kidney

Excretory System Labelling and Function Questions

Label the structures of a nephron:

Match the part of the kidney tubule with its function:

collecting duct; loop of Henle; distal convoluted tubule; glomerulus; proximal convoluted tubule; renal artery; Bowman’s capsule; Antidiuretic hormone or ADH

Part of tubule Function

Carries blood to the kidney

The hormone that is involved in producing concentrated urine

Cup shaped structure through which the fluid part of the blood is filtered

Where the majority of water is extracted from the urine

Looped portion of the tubule. Important for helping concentrate the urine

Where hydrogen and potassium ions are secreted into the urine

Glucose, salts, water and amino acids are reabsorbed into the blood

capillaries here

Tuft of capillaries carrying high pressure blood

The Role of Kidneys in Maintaining Homeostasis

Each ____________________ in your body passes through a kidney about ___________________________________.

The kidney is able to fine tune the composition of blood and thereby help maintain homeostasis

Kidney failure results in the breakdown of homeostasis and death occurs shortly thereafter (approximately 2 weeks).

The kidneys regulate the water content of the blood:

Human kidneys filter out about _______________________ of fluid from the blood each ______________________.

Without reabsorption of water you would urinate about _____________________ of water a day.

Reabsorption of water into the blood occurs through _________________ when the filtrate (fluid which has been filtered) travels through the tubule and the collecting duct.

Reabsorption is controlled by a _________________________________ that involves the amount of __________________________________ circulating in the blood. This hormone increase the permeability of the distal tubule and the collecting duct to water, allowing more water to be reabsorbed from the urine.

The release of ADH is regulated by receptor cells in the _____________________________ The release of ADH increases water reabsorption and produces urine more concentrated than the blood.

If a person does not have sufficient water, the lowered level of water in the blood signals the hypothalamus to _____________________________.

The ADH travels through the blood to the body. Upon reaching the kidney tubule it stimulates the cell membranes to become ______________________________. As a result more water is reabsorbed into the blood and the _________________________________

If a person has too much water ______________________________. Then the cell membranes of the tubules become __________________________. They do not allow water to return to the blood and __________________________________.

The Bladder

Your bladder is the ________________________________________ that collects and stores _______________________. As your bladder fills, it expands to store the urine.

On average, your bladder can hold ____________________ of urine for up to about five hours.

The muscle in your bladder wall is called the _____________________ muscle. The detrusor muscle relaxes to allow your bladder to fill. When you go to the toilet, it contracts to squeeze out urine.

Sphincters associated with Excretion:

There are two sphincter mechanisms:

The internal sphincter is a ring of muscle that holds the neck of the bladder in place. Your body opens and shuts it automatically without you thinking about it.

o Internal urethral sphincter: Smooth muscle Involuntary control More superiorly located

The external sphincter acts like a tap and keeps urine in the bladder. It is controlled by the ___________________________________________, which is controlled by the voluntary nervous system. This means it’s under your control - you decide when to let it open. The external sphincter is also called the distal sphincter.

o External Urethral sphincter: Skeletal muscle Voluntary control Posteriorly located

How do you know when to empty your bladder?

The ____________________________________ tells you when you need to empty your bladder. This happens on average _________________________ a day. The reflex is controlled by your ____________________________________________.

When your bladder is about half full, the stretch receptors in the walls of your bladder become active and send signals along your pelvic nerves to your spinal cord.

A reflex signal is sent back to your bladder, which makes the detrusor muscle in the bladder wall contract. The contraction increases the pressure in your bladder, and this is what makes you want to pass urine.

Because the external sphincter is under voluntary control, you don’t urinate until you decide to relax this muscle.

Homeostasis – Water Balance and Urine Concentration

Homeostatic mechanism involved in regulating levels of materials in the blood is called ___________________________________ and involves two very important hormones: ______________________________ Hormone (ADH), and _______________________.

_______________________________ hormone (ADH): Maintains __________________________ balance in the body. When the __________________________ in the brain detects a lowering of

__________________________________ in the body. it signals the_________________________ gland to release ADH into the

_________________________ ADH increases the reabsorption of ____________________ by the kidneys (by

_____________________ the permeability of the ________________________). If too much______________ is present, the hypothalamus decreases the

secretion of __________________

↑ADH = ______________________________

Aldosterone: Maintains ________________________________ in the body. ______________________ drops when the level of ________________in the blood falls. _____________, an enzyme produced by the ______________ causes the

______________ gland to release the hormone aldosterone promotes the reabsorption of _____________________ Blood vessels ________________, blood pressure rises as a result, __________

is released, and a sensation of _______________ are all part of this process. When _________________________ and __________________ concentration in the

blood returns to normal, renal ____________________ secretion is turned off.

↑Na+ reabsorption = ___________________

Diuretics: Diuretics _____________________the output of urine, leaving the body below normal

____________________ levels: Caffeinated Beverages: Such as _________________, tea and ________________ all

stimulate arteries to ________________________, which raises blood pressure, and more water is ______________________ under pressure out of the_______________ into the nephron for excretion.

_____________________: Inhibits the flow of ________________, therefore not enough water is reabsorbed in the tubule, and water loss occurs.

Drugs: Can act as a diuretic, or an antidiuretic (opposite effects).

Urinalysis

Characteristics of urine:

• pH- 4.5-8, avg. 6.0o vegetarian diet- urine is alkalineo protein rich and wheat diet- urine is acidic

• Color- pigment is urochromeo Yellow color due to metabolic breakdown of hemoglobin (by bile or bile

pigments)o affected by what we eat: salty foods, vitaminso Beets or rhubarb- might give a urine pink or smoky coloro Vitamins- vitamin C- bright yellowo Infection- cloudy

• odor- normal is ammonia-like

Urine Tests:

A urinalysis is a group of _______________________and __________________________ tests. They detect the byproducts of normal and abnormal metabolism, cells, cellular fragments, and bacteria in urine.

Urine is produced by the ____________________, two fist-sized organs located on either side of the spine at the bottom of the ribcage. Urine is generally _____________________ and relatively clear, but each time someone urinates, the color, quantity, concentration, and content of the urine will be slightly different because of varying _________________________.

Many ________________________can be diagnosed in their early stages by detecting _________________________________ in the urine. Abnormalities include increased concentrations of constituents that are not usually found in significant quantities in the urine, such as: glucose, protein, bilirubin, red blood cells, white blood cells, crystals, and bacteria.

They may be present because:1. ________________________________________________________________________

________________________________________________________________________________________________________________________________________________

2. ________________________________________________________________________________________________________________________________________________

3. ________________________________________________________________________________________________________________________________________________

How is it used?

The urinalysis is used as a screening and/or diagnostic tool because it can help detect substances or cellular material in the urine associated with different metabolic and kidney disorders. It is ordered widely and routinely to detect any abnormalities that require follow up.

Often, substances such as _______________________ or ______________________ will begin to appear in the urine before patients are aware that they may have a problem. It is used to detect ______________________________________________ and other disorders of the urinary tract. In patients with acute or chronic conditions, such as kidney disease, the urinalysis may be ordered at intervals as a rapid method to help monitor organ function, status, and response to treatment.

Abnormal Constitutes of Urine

1. Glucose- when present in urine condition called ________________________ (non-pathological). [Glucose not normally found in urine]

Indicative of:• __________________________________________• __________________________________________• __________________________________________

2. Albumin-abnormal in urine; it’s a very large molecule, too large to pass through glomerular membrane. Condition called ___________________________________

o Non-pathological conditions- • _______________________________________• pregnancy• overabundant protein intake-- leads to physiologic albuminuria

o Pathological condition• kidney trauma due to blows• ______________________________________• ______________________________________

What does the test result mean?

Generally, the _______________________the concentration of the atypical substance, such as greatly increased amounts of glucose, protein, or red blood cells, the _____________________ it is that there is a problem that needs to be addressed.

A normal urinalysis does not guarantee that there is no illness. Some people will not release elevated amounts of a substance early in a disease process, and some will release them sporadically during the day, which means that they may be missed by a single urine sample. In very dilute urine, small quantities of chemicals may be undetectable.Disorders of the Excretory System

Disorder Cause Symptom TreatmentNephritis

Cystitis/ Urinary Tract Infection

Kidney Stones

Gout

Hepatitis

Excretion Unit Review Questions

1. Describe the three main functions of the kidneys.

2. What are the functional units of the kidney?

3. List the functions of the following structures:

o Glomerulus o Bowman's (Glomerular) capsuleo Proximal convoluted tubule o Loop of Henle o Distal convoluted tubule o Collecting duct o Renal artery o Renal vein o Afferent arterioleo Efferent arteriole o Peritubular capillaries.

4. List and explain the three main processes that are involved in urine formation.

5. Place the following processes in the correct order:

a) blood enters the afferent arterioleb) fluids pass from the glomerulus into Bowman’s capsulec) sodium ions, glucose and amino acids are actively transported from the nephron to

the bloodstreamd) water is diffused from the nephron to the bloodstreame) urine is stored in the bladder.f) urine is excreted by the urethra

6. How do the blood vessels in the glomerulus contribute to filtration?

7. Explain the role of ADH in water balance.

8. How does the kidney contribute to the maintenance of blood pressure?

9. A micropipette was used to extract fluids from various structures within the kidney. The

data in the following table is an analysis of the substances collected. All quantities are in g/mL. Answer the following questions providing an explanation for each.

Substance found in body fluid

Blood plasma from afferent arteriole

Glomerular filtrate from Bowman’s capsule

Urine

protein 7.00 0.00 0.00urea 0.04 0.04 2.00glucose 0.10 0.10 0.00sodium ions 0.32 0.32 0.35

a) Which substance is not filtered from the blood into the Bowman’s capsule?

b) Which substance provides evidence of secretion?

c) Which substance provides evidence of reabsorption?

Excretion Unit Review

Amino acids are broken down into what?

What two products make up urea? Where does this reaction take place?

Approximately how much does the average person expel as urine at once?

Draw the excretory system. Include: Kidney, Ureter, Urinary Bladder, Urethra

Draw a nephron. Include: Afferent Arteriole, Efferent Arteriole, Bowman’s Capsule, Glomerulus, Proximal Convoluted Tubule, Ascending and Descending Loop of Henle, Loop of Henle, Distal Convoluted Tubule, Collecting Duct, Medulla, Cortex

Draw a kidney. Include: Cortex, Medulla, Renal Artery, Renal Vein, Renal Pelvis, Ureter

Go through the steps and definitions of filtration and reabsorption in a nephron. In other words, explain the function of each of the parts of the nephron.

What molecules does the body not want to filter out, and therefore reabsorbs nearly 100% of (should be absent in the urine)?

Name the 3 excretory diseases. Describe them in your own words.