The Digestive and Excretory
Systems
Nutrition
• Nutrition is the science or study of how our
bodies obtain energy, build tissue, and control
body functions using materials supplied in the
food we eat
• Food contains nutrients (molecules that provide
energy and material for growth and repair)
• Humans are heterotrophs-obtain their food
• Autotrophs (i.e. Plants) are capable of producing
their own food
Types of Nutrients
• Organic nutrients include carbohydrates,
proteins, lipids , and vitamins
• Inorganic nutrients include water and minerals
• Scientists refer to the energy stored in food as
dietary calories
• Adolescent females require about 2200 calories
per day and males require about 2800 per day
• A balanced diet includes foods from the four
basic food groups: vegetables and fruit, grain
products, dairy products, and protein-rich foods
Nutrients Continued
Carbohydratesmost of the energy
made up of Carbon, Hydrogen, and
Oxygen (1:2:1 ratio)
sugars and starches
monosaccharides, disaccharides, and
polysaccharides
Nutrients Continued
ProteinsProvides the body with material necessary for
growth and repair
Made up of amino acids
Lipids or Fats
Your body does need a certain amount of fat in
order to be healthy
Three fatty acids joined to a Glycerol molecule
Saturated fats or Unsaturated fats
Nutrients continued
VitaminsDo not contain energy
Water -soluble and fat- soluble
Needed by the body in very small amounts that
serve as coenzymes
Play a role in cellular reactions
When the body does not receive a sufficient
supply , it can develop a vitamin deficiency
Minerals –
Inorganic substances required by the body for
normal functions
Nutrients continued
A balanced diet usually provides all the necessary
minerals
WaterEssential nutrient and most important
Most of our bodies weight is water
Solvent
We lose between 3-5 L of water through sweat,
urine, and exhaled air
Dehydration
Digestion
• The Digestive System includes: the mouth, the
pharynx, esophagus, stomach, small intestines,
and large intestines
• Several major accessory structures include
salivary glands , the Pancreas, and the Liver all
add secretions to the digestive system
• The function of each organ of the digestive
system is to help convert foods into simpler
molecules that can be absorbed and used by the
cells of the body
Path of Digestion
Food is ingested through the mouth. It is here where
food is broken down into chewable and swallow
able chunks by the teeth and the tongue
(mechanical digestion). The teeth do much of the
mechanical digestion by cutting, tearing, and
crushing food into smaller fragments. The
salivary glands secrete saliva, which helps to
moisten food and make it easier to chew.
Amylase is an enzyme that breaks down chemical
bonds between the sugar monomers and the
starches.
• Pharynx-the food then passes from the mouth or
oral cavity into the pharynx. As the tongue moves
food into the pharynx, it presses down on a small
flap of cartilage called the Epiglottis. Once in the
Pharynx swallowing becomes involuntary and
the medulla is the part of the Brain the controls
swallowing.
• Esophagus-food is then passed through the food
tube or esophagus and into the stomach. The food
moves down the esophagus by involuntary
muscle contractions known as peristalsis.
Path of Digestion
• The sphincter closes the esophagus after food
passes into the stomach and prevents contents
from moving back up.
• Reverse peristalsis
• Stomach-food enters the stomach from the
esophagus. The stomach contains microscopic
gastric glands that release mucus, hydrochloric
acid, and gastric juices. Pepsin is also produced ,
especially useful for protein digestion.
• Ulcers are lesions of the digestive tract lining
Path of Digestion
• The semi-liquid mass of partially digested food
known as Chyme enters the duodenum and into
the small intestines.
• Pancreas-the presence of chyme in the duodenum
causes the release of pancreatic fluid from the
pancreas. The pancreas is a gland that formed by
the duodenum and under the surface of the
stomach. The pancreas produced hormones that
regulate blood sugar levels, produces enzymes
that break down carbohydrates, proteins, lipids,
and nucleic acid.
Path of Digestion
• Liver- assists the pancreas and produces bile. Bile
helps to neutralize the chyme from the stomach
and emulsifying fats. Bile is stored in the gall
bladder.
• Small Intestines- made up of the duodenum,
jejunum, and the ileum, specially adapted to
absorb nutrients because it is covered with villi.
• The Large Intestines-main job is to reabsorb
water and electrolytes. Diarrhea occurs when
there is interference with water absorption.
Today’s Agenda
• Aim: What is the job of the excretory
system?
• Do Now
• Class Discussion
• Group work
• Closing
The Excretory System
DO NOW
How is the process of preparing a pot of
coffee using a coffee filter, ground coffee,
and boiling water similar to the processes
involved in human excretion?
The Human Excretory System
The excretory system plays a major role in
maintaining homeostasis
The organs of excretion are the skin, lungs,
and kidneys
The liver may also be considered an organ
of excretion
Carbon dioxide, urea, water, and salts are
all metabolic wastes produced by humans
The Skin
 Epidermis (outer layer) protects dermis
Dermis (inner layer)
Sebaceous glands-produce oils
Sweat glands-produce sweat that is
released through holes called pores
Helps to remove excess heat because
evaporation of sweat cools the body
The Lungs
• Upon exhaling the lungs rid the body of
carbon dioxide and water vapor
The Kidneys
• Main organ of the excretory system
• 2 kidney’s located on either side of the spinal
column near the lower back
• Play a role in maintaining homeostasis by
regulating the water content of the blood, and,
therefore, blood volume, maintains blood pH,
and removes waste products from the blood
• Urine (urea, water, salts, and other waste
products)
• Filtration and reabsorbtion
The Urinary System
• The kidneys, ureters, the bladder, and the
urethra
• Urine passes from each kidney through the
ureter to the urinary bladder where it is
stored
• During urination, the urine travels from the
bladder to the outside of the body through
the urethra during urination
Structure of the Kidney
• 3 main parts of the kidney: cortex ( the outer
part), the medulla ( the middle part) , and the
pelvis ( inner region)
• Renal artery and renal vein supply kidneys with
blood
• Over 1 million nephrons
• Each nephron is made up of a glomerulus,
Bowman’s capsule, and a renal tubule
• The glomerulus is a network of capillaries
• Bowman’s capsule is a double walled chamber
that surrounds the glomerulus
Structure of Kidney
• Proximal tubule is a segment of the nephron
tubule where water, sodium ions, glucose, and
amino acids are absorbed
• Loop of Henle is where the proximal tubule
leads, and it is here that sodium ions are actively
transported out
• Distal tubule is where additional sodium and
water can be reabsorbed
• Collecting tubule receives urine from smaller
tubules
The Liver
• Detoxification –removes harmful waste
from the blood
• Overloading the liver with alcohol can lead
to cirrhosis and the liver becomes
overgrown with extra tissue
• Cirrhosis limits the function of the liver
and can lead to death
Interference
•
Kidney stones- substances in urine crystallize in
the urinary tract or kidney
• Gout is a disorder where uric acid builds up and
is stored in the body, usually the joints or big
toe
• Humans can survive with one kidney , but if
both are damaged by disease or injury there are
two ways to keep the person alive
1. Kidney transplant from a compatible donor
2. Dialysis
Partner Discussion
• What is the purpose of a urine test?
• What can a urine test possibly detect?