The Excretory System

By: Mike Bow, Anup Shah, Christal Alonzo

Overview: The Excretory System

• Handles movement of solute between internal fluids and external environment.

• Central to homeostasis because they dispose of metabolic wastes and control body fluid composition by adjusting rates of solute loss.

Forms of Nitrogenous Waste • Nitrogen is released after metabolic processes.

• Ammonia: Common in aquatic animals. Very soluble and toxic. Passes membranes easily and lost by diffusion (requires no energy).

• Urea: Produced in liver by combining CO2 and ammonia. Carried to kidneys. Low toxicity. Requires less water. Expends some energy.

• Uric Acid: Semisolid paste with little water loss, insoluble in water, relatively nontoxic requires large amount of ATP.

Key Functions of Excretory System• Filtration

– Fluid is filtered through selectively permeable epithelium.– Hydrostatic pressure or blood pressure is used to force

solutes and water across membrane into the excretory system, creating filtrate.

• Selective Re-absorption– Essential small molecules are recovered from filtrated and

returned to body fluids by active transport.

• Secretion– Uses active transport to extract toxins and excess ions and

add to contents of excretory tubule.

• Excretion– Processed filtrate leaves the system and the body as urine.

Types of Excretory Systems

• Vary based on network of tubules.

• Protonephridium: A network of dead-end tubules lacking internal openings. Produces dilute fluid and found in flatworms.

• Metanephridia: Has internal openings that collect coelmic fluid and enveloped by capillary network. Produces dilute urine and found in earthworms.

• Malphighian tubules: Organs found in insects and immersed in hemolymph. Produces nearly dry excretion.

• Vertebrate Kidneys: compact, non-segmented organs containing numerous tubules arranged in highly organized manner, a dense network of capillaries, and ducts.

Kidneys• Blood is supplied by renal

artery and drained by renal vein

• Contains Outer Renal Cortex and Inner Renal Medulla

• Empties into Collecting duct Renal pelvis where NaCl reabsorbed

• Urine exits through the ureter urinary bladder urethra out of body

Path of Filtrate

• Proximal tubule: Filtrate’s volume and composition are altered through secretion and absorption

• Loop of Henle:

– Descending Limb – Water moves by osmosis into the hyperosmotic interstitial fluid

– Ascending Limb – Salt diffuses out of the concentrated filtrate.

• Distal tubule: regulates K+ and NaCl concentration of body fluids

From the Bowman’s Capsule: a cup shape swelling, filtrate passes through 3 regions of the nephron: the functional unit of kidney

Blood Vessels Associated

• Glomerulus: ball of capillaries

• Afferent arteriole: branch of renal arteriole

• Efferent arteriole: converges after glomerus

• Peritubular capillaries: surrounds proximal and distal tubules

• Vasa recta: found in loop of Henle

Feedback Mechanisms of Kidneys

Is an elaborate system of checks and balances that regulate the kidney’s ability to control the osmolarity, salt

concentration, volume, and pressure of blood.

RAAS ADH

Antidiuretic horomone (ADH):

• Regulates blood osmolarity through osmoreceptors

• Stimulus: Above 300mosm/L - due to loss of water through sweating or ingestion of salty foods

• More ADH is released into blood stream, targets distal tubules and collecting ducts of kidneys

• Increases permeability of epithelium to water

• Amplifies water reabsorption and reduces urine volume

• Negative feedback – subsiding osmolarity of blood reduces activity of osmoreceptors less ADH secreted

Renin-angiotensin-aldosterone system (RAAS)

• Stimulus: Blood pressure or volume drops in afferent arterioles

• Juxaglomerular apparatus (JGA): tissue where enzyme renin initiates chemical reactions to convert the protein angiotensinogen into the peptide Angiotensin II:

– Raises blood pressure and volume by constricting arterioles and decreasing blood flow to many capillaries

– Stimulates proximal tubules to reabsorb more NaCL and water– Reduces amount of water and salt excreted in urine– Stimulates release of Aldosterone:

• Makes distal tubules reabsorb more Na+ and water• Increase blood volume and pressure

Atrial natriuretic factor (ANF)

• Opposes RAAS

• Walls of atria in heart release ANF

• Stimulus: increase blood volume and pressure

• Inhibits release of renin in JGA

• Inhibits reabsorption of NaCl by collecting ducts

• Reduces aldosterone release from adrenal glands

• Lowers blood volume and pressure

Dialysis

• Performed when kidney can no longer function properly.

• Keeps body balanced by removing waste products, keeping a safe level of chemicals in the blood, and controlling blood pressure.

1. Hemodialysis: uses an artificial kidney inserted into blood vessels or a fistula – when the artery is joined with a blood vessel.

2. Peritoneal Dialysis: blood is cleaned inside the body using a plastic tube called a catheter that fills the body with dialysate and later removes it.

Lungs

• Lungs are respiratory surfaces of terrestrial vertebrates, land snails, and spiders that connect to the atmosphere by narrow tubes and diffusion.

Human Lung

• The lungs function in gas exchange, where they excrete carbon dioxide into the environment and uptake oxygen.

How a Mammal Breathes • Mammals ventilate their lungs by negative pressure breathing, a breathing system in which air is pulled into the lungs.

• Lung volume increases as a result of contraction of the rib muscles and the diaphragm.

• Tidal volume is the volume of air a mammal inhales and exhales with each breath.

• Vital capacity is the maximum tidal volume during forced breathing.

Flow of Air in Mammals• Air enters through the nostrils

• Filtered by hairs

• Flows through the nasal cavity

• Leads to pharynx

• Into trachea (windpipe)

• Branches into two bronchi

• Leads into Bronchioles

Gas Exchange in Mammals• In the lungs, the epithelium lining of the braches is covered by cilia and mucus that

traps dust, pollen, and other contaminants.

• The beating cilia that moves the mucus upward to the pharynx, where it can be swallowed into the esophagus and excreted, thus cleansing the respiratory system.

• At the tips of the bronchioles, there is a cluster of air sacs called alveoli where gas exchange occurs across the thin epithelia.

• Oxygen dissolves in the moist film and rapidly diffuses across the epithelium into a web of capillaries that surrounds each alveolus.

• Carbon dioxide diffuses in the opposite direction, from the capillaries across the epithelium of the alveolus and into the air space

Different Methods of Gas Exchange• Occurs over the entire surface area of most protists and

other unicellular organisms.

• Sponges, cnidarians, and flatworms have plasma membranes where gases diffuse in and out.

• An earthworm has moist skin and exchanges gases by diffusion across its general body surface

• Gills, trachea, and lungs are the three most common respiratory organs

Control of Human Breathing

• Control centers in the medulla oblongata of the brain regulate the rate and depth of breathing

• Sensors detect the pH of cerebrospinal fluid, and the medulla adjusts breathing rate and depth to match metabolic demands.

Lung Diseases

• Asthma- the inside walls of your airways become sore and swollen. Causes wheezing, coughing, chest tightness and trouble breathing.

• Pneumonia- is an inflammation of the lung, usually caused by an infection. Causes difficulty breathing accompanied by a cough and a fever

• Bronchitis- inflammation of the lining of the bronchioles

• Emphysema- condition in which the alveoli deteriorate, causing the lungs to lose their elasticity

Lung Cancer

Healthy Lung Smoker’s Lung

• It is a leading cause of cancer death in men and women in the United States.

• Cigarette smoking causes most lung cancers.

Skin

One square inch of skin has:

– 65 hairs

– 100 sebaceous glands

– 78 yards of nerves

– 650 sweat glands

– 19 yards of blood vessels

– 9,500,000 cells

– 1,300 nerve endings

– 20,000 sensory cells

Human Skin• Thin epidermis on top – outer protective layer without blood

vessels

• Thicker dermis below

• Dermis - inner layer of skin with blood vessels, sensory nerve endings, oil glands, hair follicles, fatty layers, nerves, and sweat glands

• Have glands for secreting fluids on surface

Human Skin (continued)

• Excretion – excess water, salt, urea, and uric acid removed in sweat

• Waterproofing – oil glands prevent water entry as well as loss of water

• Regulation of body temperature – dermis, fat cell layer insulates body

Human Skin (continued again)

• Goosebumps – contraction of small muscles attaches to hairs creates insulation of warm air

• Sensory detection – nerve endings in dermis detect heat, cold, touch, pressure, and pain

• Protection from disease – prevents invasion of micro-organisms and dust into body

• Protection from ultra-violet rays – melanocytes produce melanin, pigments reduce effects of UV rays

Sweat Glands Secrete Sweat• Sweat is a watery fluid containing sodium-chloride, lactic

acid, urea, amino acids, and glucose

• Helps with excretion of water and sodium chloride and some urea and lactic acid

• Sweat glands have tubular structure tangled capillaries

• Proximity of tubes enables wastes to diffuse from blood into sweat glands

• Body temperature rises – sweat releases from glands, travels through duct, and escapes reaches through pores

• Cooling effect

• When the kidney fails urea is secreted by sweat glands

Sebaceous Glands

• Excretes lipids such as waxes, sterols, hydrocarbons, and fatty acids

• Secretes sebum keeps skin moist and soft and acts as a barrier

Skin Maintenance

• Keeping skin clean prevents infections and odors

• Dermatitis – caused by excess washing and loss of oil in the outer layer of the skin, chemicals that dry and irritate skin

• Ultraviolet light – major cause of skin aging

• Decreased blood supply impedes healing of damaged skin

• Avoid overbathing, use pH balanced soaps, and humectant creams and lotions

WebQuest Activity #1 – Kidneys You are a designer for video games for the XBOX

360. Create an epic game depicting the path of a filtrate through the mammalian excretory system, focusing mainly on the structures of the kidneys.

 

For example your main character could be Phil the Filtrate. He is lost in the massive body of a human! Help him return to the correct path of a filtrate by navigating through the kidneys of the excretory system.

Design different levels as certain structures of the kidney, such as traveling through the 3 main regions of the nephron. To move on to the next level in the game, create tasks, such as climbing the ascending limb of the loop of Henle. Be sure to incorporate the how the hormones of the kidneys affect the main character as he or she travels. Express the idea in an organized way, such as a detailed narrative, a flow chart, or a series of storyline drawings (like ones animators use).

WebQuest Activity #1 – Kidneys

Here are some links to help you with your task:1. http://www.kidney.org/2. http://health.howstuffworks.com/kidney1.htm 3. http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Bi

oBookEXCRET.html4. http://www.franklininstitute.org/learn/heart/systems/excre

tion.html

5. http://biology.clc.uc.edu/Courses/bio105/kidney.htm 6. http://www.healthscout.com/ency/68/637/main.html#Defi

nitionofKidneyDialysis

7. http://www.ivy-rose.co.uk/Topics/Urinary_System_Kidney_Dialysis.htm

WebQuest Activity #2 – LungsParker Bros. has decided to create an educational

game based on the excretory functions of the lungs in humans in the likeness of Monopoly.

Your task is to create a game board, with specific spaces representing important structures and their functions. For example, “the Start/Go” space could be where air enters the body, the nostrils.

 Certain spaces may be scattered on the board to

represent “trivia cards” to pick up. These cards can be used to quiz about lung disease and disorders, as well as any other mechanisms that work on the lungs.

 It should look like a basic map of the flow of air and mucus in humans, with the major structures of the lungs included.

Besides the board game, an overview of the goal of the game, guidelines and rules, and game pieces are required.

WebQuest Activity #2 – Lungs

Here are some links to help you with your task:

1. http://www.nlm.nih.gov/medlineplus/lungdiseases.html

2. http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Pulmonary.html

3. http://users.adelphia.net/~lubehawk/BioHELP!/hrespsys.htm

4. http://encarta.msn.com/encyclopedia_761574532/Amphibian_(animal).html

WebQuest Activity #3 – Skin“Just scrub it.”

This is the motto for an advertisement for the new version of a shampoo by “Herbal Essences.” Your task is to make a 2-5 minute short skit of a commercial presenting this product.

The first part of the commercial should generally talk about the main structures of the skin and its glands to introduce the customer viewers to the shampoo.

Mention reasons why a person should use your shampoo. This can include why, how, and what fluids and wastes skin secretes and excretes. Also include other selling points, such as prevention of diseases (list and describe them), infection and odors.

WebQuest Activity #3 – Skin

Here are some links to help you with your task:

1. http://www.marymount.k12.ny.us/marynet/stwbwk03/03bio/excretory/skin.html

2. http://www.pinkmonkey.com/studyguides/subjects/biology-edited/chap19/b1919301.asp

3. http://users.adelphia.net/~lubehawk/BioHELP!/hexcrsys.htm#skin

4. http://qldscienceteachers.tripod.com/junior/biology/excretory.html

5. http://www.cawc.net/open/library/education/skin-self-study.html

Resources:

1. Textbook – A.P. Biology 7th Edition by Campbell and Reece

2. Links (Pictures)

1. http://faculty.etsu.edu/currie/images/renal113.jpg

2. http://www.merck.com/media/mmhe2/figures/MMHE_03_022_01_eps.gif

3. http://openlearn.open.ac.uk/file.php/2815/S324_1_039i.jpg

4. http://members.tripod.com/gopaws/images/kidney-Dennis..gif