Homeostasis

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Homeostasis The Digestive System
Hungry???
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Nutritional requirements

• Animals are heterotrophs
• need to take in food
• Why? fulfills 3 needs
• fuel chemical energy for production of ATP
• raw materials carbon sources for biosynthesis
• essential nutrients substances animals cannot
  make themselves
• elements (N, P, K, Fe, Na, K, Ca, etc.), NAD,
  FAD, etc.

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Energy budget

basal (resting) metabolism activity
temperature regulation
food intake
ATPproduction

growth reproduction
biosynthesis

glycogen fat
storage
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• A body functions properly only when the needs of
  the organisms (water, food, heat, oxygen and
  pressure) remain within the narrowly required
  limits.
• Homeostasis The tendency to maintain a stable
  internal environment.
• Ex Furnace and air conditioner unit to maintain
  constant temperature

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• Negative feedback mechanism
• Negative feedback occurs when an increase in some
  factor is sensed and is lowered
• A response the body has to an occurrence that
  disturbs the homeostasis of the body. As the
  body reacts to that occurrence and moves closer
  to homeostasis, the receptors are shut down, thus
  causing fewer effectors to produce a product
  thats needed to bring the body back to
  homeostasis, in the end having a negative
  effect on the production. The purpose of this is
  to stop overproduction or overreaction.

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• Homeostatic mechanism in regulating body
  temperature
• Shivering in a cold environment muscles will
  contract involuntarily producing heat
• Sweating - in an overheated environment the
  brain triggers a changes that promotes the
  increased loss of body heat

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Managing glucose levels

• Human body regulates the use storage of
  glucose, a major cellular fuel
• insulin reduces blood glucose levels
• when glucose levels rise above set point,
  pancreas secretes insulin
• promotes transport of glucose into cells
  storage of glucose as glycogen in liver muscle
  cells
• dropping blood glucose levels
• glucagon increases blood glucose levels
• when glucose levels drop below set point,
  pancreas secretes glucagon
• promotes breakdown of glycogen release of
  glucose into the blood
• increasing blood glucose levels Show PDF of
  insulin

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Regulation Maintaining Homeostasis

• Balancing glucose levels in blood

glucose uptake
pancreas
insulin
depress appetite
glucose storage
glucose release
pancreas
stimulatehunger
glucagon
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Essential Nutrients

• What happens if an animals diet is missing an
  essential nutrient?
• deficiency diseases
• scurvy vitamin C (collagen production)
• rickets vitamin D (calcium absorption)
• blindness vitamin A (retinol production)
• anemia vitamin B12 (coenzyme function)
• kwashiorkor protein deficiency

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Digestion

• The reduction of large food molecules into
  smaller absorbable units and conversion of
  insoluble units into soluble ones.
• This is accomplished by mechanical action,
  chemical and enzymatic action.
• Enzymes are synthesized by cells in the mouth,
  stomach, pancreas and small intestine

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• Normally 92- 95 of a diet is digested and
  absorbed, but the process varied for each nutrient

http//www.ama-assn.org/ama/pub/category/7155.html

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Types of digestive action

• Mechanical
• Movement of the teeth grinding the food in the
  mouth
• Chemical
• Changing the food molecules into new and
  different molecules
• Lipids Lipase Fatty acids
  glycerol

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Alimentary Tract

• Alimentary canal
• A muscular tube about 9 meters long
• Appendage organs include
• Liver, biliary tree and pancreas
• Extends from the mouth to the anus
• Receives food . . . Digestion/absorption occurs .
  . .transport to cells . . .excretion of waste

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Diagram of Alimentary canal

• Peristalsis propelling movements which are a
  forward motion that is wavelike
• Peristalsis pushes tubular contents ahead of it
  through the alimentary canal

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Mouth

• Teeth mechanically grind and crush food
• Saliva moistens and binds food mass
• Salivary amylase begins digestion of starch
• Chewed food mass bolus
• Passes from mouth into esophagus
• Movement is controlled by peristalsis

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• Approximately 1.5 liters of saliva are produced
  daily by salivary glands ( 6 cups) Figure 12.1
• Amylase is a digestive enzyme
• It splits starch and glycogen (both
  carbohydrates) into disaccharides via hydrolysis
• Mucus binds food particles and acts as a
  lubricant in swallowing
• Esophagus straight tube that provides a
  passageway between the pharynx and stomach

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Stomach

• Chemical digestion begins in the middle of the
  stomach mixing food with gastric juices
• Gastric juices contain HCl, intrinsic factor,
  pepsinogen, gastric lipase mucus
• Food becomes semi-liquid chyme (50 water)
• Stomach is emptied in 1 4 hours
• Sphinctervalves at either end of stomach

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• The lining of the stomach is covered with
  numerous small holes. These are the openings of
  gastric pits which extend into the mucosa forming
  gastric glands.

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• Stomach helps to initiate the digestion of
  proteins, but also helps speed up the digestion
  of carbohydrates and fats
• Pepsin is the most important digestive enzyme in
  the stomach
• Pepsin is a protein-splitting enzyme
• It carries on a limited amount of absorption

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• The pyloric sphincter (pylorus) is a muscle that
  acts as a valve to prevent regurgitation of food
  from intestines back into the stomach

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Rugae thick folds in stomach wall
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Pancreas

• Functions as an endocrine gland
• Releases hormones
• Functions as an exocrine gland
• Secretes digestive juices
• Pancreatic juices move into the intestine
  (duodenum)
• Contains enzymes that digest carbohydrates, fats,
  proteins and nucleic acids

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• Viewing the digestive system in the anatomical
  position, the pancreas is found in under the
  stomach in the left hypochondriac epigastric
  regions

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Liver

• Located below the diaphragm in the right
  hypochondriac and epigastric regions of the
  abdominal area.

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• The liver metabolizes carbohydrates lipids and
  proteins
• Stores glycogen, vitamins A, D, B12 and iron
• Filters blood
• Detoxifies blood
• Secretes bile
• An Introduction to the Liver PDF File

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Other functions of the liver

• Producing quick energy when it is needed 
• Manufacturing new body proteins 
• Preventing shortages in body fuel by storing
  certain vitamins, minerals, and sugars 
• Regulating transport of fat stores 
• Regulating blood clotting 
• Aiding in the digestive process by producing
  bile 
• Controlling the production and excretion of
  cholesterol 
• Neutralizing and destroying poisonous
  substances 
• Metabolizing alcohol 
• Monitoring and maintaining the proper level of
  many chemicals and drugs in the blood 
• Cleansing the blood and discharging waste
  products into the bile 
• Maintaining hormone balance 
• Serving as the main organ of blood formation
  before birth 
• Helping the body resist infection by producing
  immune factors and by removing bacteria from the
  bloodstream 
• Regenerating its own damaged tissue and 
• Storing iron.

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• Bile -
• Yellowish, green liquid made of bile salts, bile
  pigments, water, cholesterol and electrolytes
• Bile salts aid the digestive enzymes and enhance
  the absorption of fatty acids and fat-soluble
  vitamins
• Bile salts act as emulsifiers, breaking up fat
  into droplets, allowing lipases to digest them
  better

5.1.3 state source of one lipase substate,
source and optimum pH
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• Bile is stored in the gall bladder until a
  hormone stimulates its release into the small
  intestines

http//www.foxriverwatch.com/liver_hepatic_damage_
pcbs_1a.html
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Small Intestine

• Approx. 20 -25 feet long with villi and
  microvilli for a total surface area of 25 sq
  meters
• 3 areas
• Duodenum
• Jejunum
• Ileum
• Most digestion occurs in the duodenum
• Most absorption occurs in the jejunum and ileum

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• The intestines are lined with villi
• Increase the surface area of the intestinal
  lining
• Increase the absorption of digestive products
• Capillaries carry away absorbed products from
  villi
• Nutrients are absorbed by several means
• Simple diffusion (higher to lower concentration
  area)
• Facilitated diffusion (Against the gradient using
  channel or carrier proteins)
• Active transport (diffusion with ATP)

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• Microvilli on intestinal epithelial cells

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• As chyme enters duodenum it stimulates the
  release of pancreatic juices and mixes with
  enzymes from the pancreas and small intestine as
  well as with bile, fluid and bicarbonates
• All the gastric, small intestinal secretions and
  pancreatic secretions are controlled by the
  nervous system and by hormones

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Digestive enzymes in sm. intestine

• Enzymes are specific to a particular substrate
• Proteins
• Peptidases break peptides into amino acids
• Lipids
• Lipases break lipids into glycerol and fatty
  acids

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Carbohydrate Digestion

• Begins in mouth with salivary amylase
• Halted by hydrochloric acid
• Digestion mostly occurs in small intestine by
  pancreatic amylase
• Passes through intestinal wall in monosaccharide
  form (ex glucose)

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• They quickly move through the digestive system
• Some carbohydrates cannot be digested by humans
  and are excreted
• They provide short term energy

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Protein Digestion

• Begins in stomach by proteolytic enzymes
• Most of digestion takes place in the duodenum by
  pancreatic and intestinal enzymes Protein
  hydrolysis
• Final phase occurs in the brush border of the
  microvilli
• Absorbed in the amino acid form
• Allergic reactions can occur when intact proteins
  pass through intestinal wall

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• Proteins move through digestive system 2nd
  fastest after carbohydrates
• Once protein is broken down into amino acids,
  these are reassembled into 1º,2º,3º and 4º
  proteins the body needs
• Hemoglobin blood protein
• Albumin in plasma aids in blood clotting
• Fibrinogen blood clotting agent

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Lipid Digestion

• Begins in stomach with gastric lipase
• Major digestion occurs in small intestine
• Bile and action of stomach/small intestine break
  down large globules into smaller pieces
• Lipase breaks down particles into fatty acids.
• Cholesterol and fat soluble vitamins follow
  similar process

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• Lipids move slowly through the digestive system
• They are stored as long term storage in the form
  of adipose tissue

http//www.sunyniagara.cc.ny.us/val/adipose2.html
http//www.gen.umn.edu/courses/1135/lab/kidneylab/
kidneylab.html
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Vitamins, Minerals and Fluids

• Absorbed in the intestine
• Eight liters of fluid are passed back and forth
  across the membrane of small intestine to keep
  nutrients in solution
• Vitamins and water pass unchanged from small
  intestinal wall into the blood stream
• Absorption of mineral occurs in stages in small
  intestine

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Large Intestine

• Includes
• Ascending colon
• transverse colon
• descending colon
• sigmoid colon
• rectum

http//www.fruit-eze.com/education/colon/
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• Large intestine primarily absorbs water,
  electrolytes and some vitamins
• Bacteria break down undigested material
• Formation and absorption of vitamin K
• Formation and excretion of waste products

http//www.fujinon.com/product/medical/ed0114.htm
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• Little digestion now occurs as it is mostly
  completed by this time.
• Large intestine are about 5 feet long
• Mixing movement and peristalsis occur but are
  much slower here.
• Peristalsis occurs only 2 to 3 times/day.

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• Contain E. Coli (good form not 0157) that break
  down remaining food and aid in the formation of
  vitamin K
• Newborns and vitamin K
• The solid waste consists of dead bacteria,
  undigested fiber and other products of digestion.