The Digestive and Excretory Systems

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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

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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

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Nutrients Continued

• Carbohydrates-
• most of the energy
• made up of Carbon, Hydrogen, and Oxygen (121
  ratio)
• sugars and starches
• monosaccharides, disaccharides, and
  polysaccharides

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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

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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

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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

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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

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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.

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• 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.

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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

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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.

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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.

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Todays Agenda

• Aim What is the job of the excretory system?
• Do Now
• Class Discussion
• Group work
• Closing

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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?

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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

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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

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The Lungs

• Upon exhaling the lungs rid the body of carbon
  dioxide and water vapor

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The Kidneys

• Main organ of the excretory system
• 2 kidneys 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

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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

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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, Bowmans
  capsule, and a renal tubule
• The glomerulus is a network of capillaries
• Bowmans capsule is a double walled chamber that
  surrounds the glomerulus

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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

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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

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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
• Kidney transplant from a compatible donor
• Dialysis

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Partner Discussion

• What is the purpose of a urine test?
• What can a urine test possibly detect?