DigestiveExcretory

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Digestive/Excretory

• Read 720-738
• HW 740

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Digestion

• Remember that all living things need to use
  energy. Digestion converts nutrients, substances
  the body needs, into useable material for growth,
  repair, and maintenance.
• There are two main parts to digestion
• Mechanical breakdown
• Chemical breakdown

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Vitamins and Minerals

• Vitamins are organic molecules that the body
  needs but do not provide energy.
• Minerals are inorganic molecules that are
  essential for proper body function.

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The process

• Digestion in humans begins in the mouth.
• The mouth provides mechanical breakdown of large
  foods and mixes it with enzymes in the saliva.
• Teeth are specialized into some that grind and
  some that rip and tear.
• The tongue allows for controlled movement of food
  inside the mouth

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Down the throat

• The throat is a combination of the pharynx and
  the esophagus.
• As we saw in the fetal pig, the epiglottis is a
  small flap of cartilage that blocks food from
  wrongly entering the windpipe.
• Muscles surrounding the esophagus aid in pushing
  food down using waves of smooth muscle
  contractions called peristalsis.

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The stomach

• The stomach is a muscular sac where more
  mechanical digestion occurs.
• Hydrochloric acid (HCl) and pepsin do a majority
  of the chemical breakdown in your stomach.
• After approximately 3 hours, food is converted
  into chyme and can be slowly passed to the
  intestines.

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Intestinal marathon

• Small intestines absorb fats, carbohydrates,
  proteins, and other nutrients.
• The human small intestine is roughly 7m long.
• Villi, short finger-like projections within the
  intestine increase surface area to increase
  absorption rate.
• Large intestines absorb water and water-soluble
  vitamins.
• The human large intestine is roughly 1.5m long.
• What doesnt get reabsorbed at this point becomes
  feces and is sent to the rectum.
• From mouth to anus, the journey can take 8 to 48
  hours.

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Accessory Organs

• The liver is one of the largest organs inside the
  body. It produces bile, a digestive fluid.
• The liver also processes carbs, fats, and
  proteins. The liver also breaks down alcohol,
  drugs, and other toxins.
• The gallbladder is connected to the liver and
  stores bile. It helps make fat easier to digest.
• The pancreas secretes fluid into the small
  intestine. Insulin is also produced here.

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Calories

• A calorie is a a measure of energy.
• One calorie is measured by the energy required to
  raise 1 gram of water 1 ºC.
• Typically in foods, we use kilocalories (1000
  calories) which are also known as Calories
  (capitalized C at all times).

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Excretion

• A way to remove produced wastes.
• Skin and digestive system do some removal
• Wastes are typically nitrogen based from
  breakdown of proteins and nucleic acids
• Wastes come in three forms
• Ammonia- diffusible into water
• Uric acid- semisolid semiliquid form
• Urea- diffusible into water (created from ammonia)

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Human excretory system

• The main organ is the kidney
• The kidney filters blood to remove wastes and
  processes it into urine.
• The kidneys also control salt, water, mineral,
  and vitamin balances while regulating pH.
• At any given time, up to 25 of the bodys blood
  may be in the kidneys.

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Afterwards

• After the kidney, urine flows through the ureters
  to the bladder.

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The kidney up close

• Kidneys are comprised of nephrons.
• The glomerulus, a clump of capillaries, works
  with Bowmans capsule to filter blood.