THE DIGESTIVE SYSTEMmmmmmm!

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THE DIGESTIVE SYSTEMmmmmmm!
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FUNCTIONS OF THE DIGESTIVE SYSTEM

• 1. INGESTS FOOD - takes in food
• 2. DIGESTS FOOD -breaks it down physically and
  chemically
• 3. ABSORBS NUTRIENTS - into the bloodstream
• 4. DEFECATES WASTE - rids body of indigestible
  items

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DIGESTIVE SYSTEM
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2 MAIN GROUPS OF THE DIGESTIVE SYSTEM

• 1. ALIMENTARY CANAL- (GASTROINTESTINAL TRACT)-
  does all the functions of the digestive system
• 2. ACCESSORY ORGANS- assist in breaking down
  food in a variety of ways (physically and
  chemically)

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• ALIMENTARY CANAL - ( aliment means" to
  nourish)
• 1 Continuous hollow coiled muscular tube which
  is open to the environment at both ends.
  MOUTH-PHARYNX-ESOPHAGUS-STOMACH- SMALL
  INTESTINE-LARGE INTESTINE-ANUS
• 2. approx. 30 feet long in cadavers
• 3. Inner lining of each organ is epithelial
  cells
• 4. Surrounded by smooth muscle tissue

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INCLUDES THE FOLLOWING

• ACCESSORY ORGANS- SALIVARY GLANDS- TEETH-
  PANCREAS- LIVER- GALL BLADDER-

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MOUTH- mucous membrane lining of epithelium

• LIPS
• CHEEKS
• HARD PALATE- palatine bone (front of mouth)
• SOFT PALATE- fleshy- located behind
• UVULA- tiny projection on soft palate that aids
  in swallowing
• TONGUE- muscle which helps maneuver food around
  and involved in swallowing
• LINGUAL FRENULUM- membrane which secures the
  tongue to the floor of the mouth

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DIGESTIVE ACTIVITIES OF THE MOUTH

• INGESTION of food, physically broken down by
  teeth, starch is chemically broken down by
  SALIVARY AMYLASE
• SWALLOWING- food is forced by the tongue back
  into the pharynx- once in the pharynx it is out
  of our control

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PHARYNX-

• posterior to the mouth where food canals and air
  canals become separated-
• Contains two skeletal muscles which are used in
  swallowing
• EPIGLOTTIS- connective tissue fold that covers
  the trachea prevents choking

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ACTIVITIES OF THE PHARYNX

• tongue blocks of the mouth, soft palate closes
  off the nasal passages, epiglottis covers the
  trachea passage food (BOLUS) enters esophagus

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4 LAYERS of TISSUE

• MUCOSA OF EPITHELIAL CELLS- mostly simple
  columnar cells used for absorption except for the
  esophagus which has stratified squamous used for
  protection
• SUB-MUCOSA- connective tissue supplies blood and
  nerves
• MUSCULARIS EXTERNA- 2 layers of muscles
• INNER LAYER IS CIRCULAR,
• OUTER LAYER IS LONGITUDINAL
• 4. SEROSA- slippery and protects the organ from
  friction (VISCERAL PERITONEUM)

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ACTIVITIES OF THE ESOPHAGUS

• PERISTALSIS- moves food toward stomach by first
  contracting longitudinal muscles then by
  contracting circular muscles- this occurs even
  without the use of gravity-

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ESOPHAGUS-

• Runs from the pharynx through the diaphragm down
  to the stomach (approx 10 inches long) contains
  smooth muscle both circular and longitudinal to
  force food through the canal.

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STOMACH FACTS

• large C shape- located on the left side of your
  body
• -storage tank and site for food breakdown
• -approximately 25 cm (10 inches) long
• -when full it can hold about 4 liters (1 gallon)
  of food

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3 MUSCLE LAYERS

• has a third layer of muscle that allows it to
  churn and mix food
• LONGITUDINAL
• CIRCULAR
• OBLIQUE

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Activities that occur in the Stomach

• 2-3 liters of gastric juice are produced daily
• 3 muscle layers of the stomach break food apart
  physically and mix it with enzymes- forms CHYME
• Gastric juice has a pH of 2 which along with the
  protein digesting enzymes would eat away the
  stomach lining (ULCER)
• MUCUS- lines the stomach to protect it

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Activities that occur in the Stomach

• Only protein digestion occurs in the stomach
• NO ABSORPTION OCCURS- except alcohol and aspirin
• Typically takes a meal 4 hours to completely
  empty from the stomach
• Chyme exits the stomach about 3 ml at a time.

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STOMACH-

• REGIONS OF THE STOMACH
• 1. CARDIAC- closest to the esophagus
• 2. FUNDUS- located above the cardiac
• 3 BODY- large base
• 4. PYLORUS- last part of the stomach

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PARTS OF THE STOMACH

• PYLORIC SPHINCTER (VALVE)- controls the opening
  to the small intestine
• RUGAE- large folds on the inner lining of the
  stomach
• GREATER CURVATURE- lateral curve of the stomach
• LESSER CURVATURE- medial curve of the stomach

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PARTS OF THE STOMACH

• GREATER AND LESSER OMENTUM- double layer of
  peritoneum which covers all abdominal organs and
  attaches them to the body wall
• - filled with fat
• - insulates, cushions and protects organs
• - many lymph nodules of the immune system for
  protection

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HEART BURN

• Food and digestive juices move back through the
  cardioesophageal sphincter and burn the esophagus

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Activities of the Stomach- GASTRIC PITS- ESSAY

• 1. GASTRIC PITS -special cells found in the
  lining of the stomach are activated by nervous
  system (sight, smell, and taste of food)
• 2. STOMACH- Cardioesophageal sphincter opens in
  the presence of food and allows it in.
• 3. Presence of food causes the release of the
  hormone GASTRIN- Gastrin causes the production
  of GASTRIC JUICES PEPSINOGEN, HCL, and mucus.
• 4. HCL bonds with PEPSINOGEN to make PEPSIN.
  PEPSIN is the major protein digesting enzyme.
  Also RENNIN an enzyme to digest protein in milk
  is produced.

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VOMITING

• is a reverse peristalsis of the stomach along
  with contraction of the diaphragm and abdominal
  muscles
• Does not occur once substances leave the stomach
  and enter the small intestine

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SMALL INTESTINE

• SMALL INTESTINE- longest organ (up to 20 feet)
• nearly all food digested here- carbohydrates,
  proteins, nucleic acids, fats
• -when duodenum is full no more chyme enters
• -3-6 hour journey

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How the Small intestine works

• PERISTALSIS- wave- like contractions
• SEGMENTATION- single segments alternately
  contract and relax - food will go back and forth
  in both directions- helps to mix the food with
  as many enzymes as possible

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3 structures that increase area in small
intestine (pg 440)

• 1. Circular Folds- (PLICAE CIRCULARES) deep
  folds
• 2. Villi- long simple columnar cells that look
  like fingerlike projections
• 3. Microvilli- hairlike projections from each
  villi

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The Small Intestine
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3 SUBDIVISION OF THE SMALL INTESTINE

• 1. DUODENUM- first 10 inches- (where ducts from
  accessory organs are connected)
• 2. JEJUNUM- middle 8 feet
• 3. ILEUM- last 12 feet of the sm. intestine
• ILEOCECAL VALVE- leads to the large intestine

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Parts

• PANCREATIC DUCTS- from the pancreas
• COMMON HEPATIC (BILE) DUCT- from the liver and
  gall bladder
• HEPATOPANCREATIC DUCT- where pancreatic duct and
  common bile duct connect before entering duodenum

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LARGE INTESTINE-

• -larger in diameter than small intestine
• -only 5 feet in length
• - Absorbs as much remaining water as possible

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ACTIVITIES OF LARGE INTESTINE

• -12-24 hour journey
• 3-4 large movements a day typically after a
  meal
• - No digestive enzymes but does have resident
  bacteria that dissolve remaining nutrients,
  produce gas and makes vitamin K an some B
  vitamins

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SUBDIVISIONS

• 1. CECUM- 1st part located below ileocecal
  valve. (sac-like)
• APPENDIX- fingerlike projection hanging from the
  cecum- unknown function
• COLON- majority divided into 4 sections
• 4. RECTUM- vertical pouch located against the
  sacrum-generally empty-
• 5. ANAL CANAL- opens to the exterior via the
  anus.

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SUBDIVISIONS OF THE COLON

• 1. ASCENDING COLON-
• 2. TRANSVERSE COLON-
• 3. DESCENDING COLON-
• 4. SIGMOID COLON- last upward curve toward the
  rectum.

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ACTIVITIES OF DIGESTION

• FECES- which contains undigested food,
  (cellulose or fiber), mucus and millions of
  bacteria and enough water for a smooth passage
  through the rectum
• When feces enter the rectum causes the DEFECATION
  REFLEX- sigmoid colon and rectum contract and
  involuntary anal sphincters relax putting
  pressure on voluntary anal sphincters.

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ACCESSORY ORGANS

• SALIVARY GLANDS- (3) produce salivary amylase
• Parotid Gland- duct to upper cheeks near 2nd
  molar- located in back of soft palate
• Sublingual Gland- duct to floor of mouth-
  located in front of lower jaw
• Submandibular Gland- duct to sides of lingual
  frenulum- located in back of lower jaw

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ACCESSORY ORGANS

• TEETH- used in MASTICATION (chewing)
• INCISORS- front 4- sharp for cutting
• CANINES- fanglike 2- used for tearing
• BICUSPIDS (PREMOLARS)-4
• MOLARS-6 used for grinding

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ACCESSORY ORGANS

• TEETH- two sets
• DECIDUOUS- 20- should have a full set by age 2
• PERMANENT-32- begin appearing between age 6 and
  12 the last set of molars WISDOM TEETH emerge
  between ages 17 and 25

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Parts of the tooth

• CROWN- above the gumline (gingiva)
• NECK- at the gumline
• ROOT- below the gumline
• ENAMEL-outer white covering- hardest substance in
  the body- mostly calcium salts
• DENTIN- bone like second layer forms majority of
  tooth
• PULP- contains blood vessels and NERVE ENDINGS
• CEMENTUM-covering of the root attaches to
  periodontal membrane
• PERIODONTAL MEMBRANE- ligament the holds teeth in
  place

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PARTS OF A TOOTH
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ACCESSORY ORGANS

• PANCREAS- soft pinkish gland- extends from
  spleen to duodenum of sm. intestine
• Creates
• 1. PANCREATIC JUICES- for digestion
• 2. INSULIN- hormone that decreases blood sugar
  levels
• 3. GLUCAGON- hormone that increases blood sugar
  levels
• Hypoglycemic- low levels of glucose
• Hyperglycemic- high levels of glucose

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Activities in small intestine

• The presence of chyme in small intestine
  activates the release of digestive juices
• PANCREATIC JUICE
• PANCREATIC AMYLASE- DIGESTS CARBS
• TRYPSIN, CHYMOTRYPSIN- DIGESTS PROTEIN
• LIPASES- DIGESTS LIPIDS (FATS)
• NUCLEASES- DIGESTS NUCLEIC ACIDS
• BICARBONATE- NEUTRALIZES STOMACH ACID

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The Liver
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LIVER AND GALL BLADDER

• LIVER- largest gland in the body
• - contains four lobes
• - most of it is located on the right side but
  it also overlies and covers most of the
  stomach
• - held to diaphragm by the FALCIFORM LIGAMENT
• GALL BLADDER- small thin-walled sac that hides
  underneath liver- stores excess bile-until
  activated by duodenum hormone CHOLECYSTOKININ-

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Activities of small intestine

• BILE- yellow-green solution made by the Liver
  and stored in the Gall Bladder- contains no
  enzymes but helps break large fat globules into
  smaller fat molecules (EMULSIFICATION)

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ACCESSORY ORGANS

• ROLE OF THE LIVER IN METABOLISM
• 1. Digestion (minor role) produces BILE when
  activated by hormone- SECRETIN
• 2. Detoxifies drugs and alcohol
• 3. Breakdowns hormones and red blood cells
• 4. Produces cholesterol, blood clotting
  proteins, albumin
• 5. Maintains blood glucose levels - stores
  excess glucose as GLYCOGEN

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NUTRITION AND METABOLISM

• NUTRIENT- substance in food that is used by the
  body to promote normal growth or maintenance

• 6 CATEGORIES
• CARBOHYDRATES- starches and sugars derived from
  plants
• 2. LIPIDS-saturated fats- animals unsaturated
  fats- plants
• 3. PROTEINS- complete proteins from eggs, milk,
  and meat
• Incomplete proteins- from legumes, nuts,
  cereals
• (1-3 are used for energy and are considered major
  nutrients)
• 4 VITAMINS- most vitamins act as a coenzyme to
  breakdown
• 5 MINERALS- have various roles (see Appendix C
  in the book)
• (4-5 are needed in minute amounts)
• 6 WATER-

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NUTRITION AND METABOLISM

• METABOLISM- all the chemical reactions
  necessary to maintain life
• CATABOLISM- the breaking down of molecules
  (energy is released)
• ANABOLISM- the building up of molecules
  (energy is needed)
• ATP- the molecular source of all energy
• CELLULAR RESPIRATION
• 1 glucose molecule ? glycolysis? Krebs cycle ?
  electron transport chain? 38 ATP

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Carbohydrate metabolism

• USAGES----Is the preferred fuel to produce
  cellular energy.
• GLUCOSE- (blood sugar) is used to make ATP in
  most cells of the body 4 kcal / gram
• Typical blood sugar 100 mg glucose / 100 ml of
  blood)

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FAT METABOLISM

• USAGES- energy storage, myelin sheath, and
  cushioning of organs
• LIVER- controls fat metabolism
• Fats are used as the reserve energy source. When
  glucose is absent in the cell then fat can be
  broken down into ATP.
• 1Gram of fat yields twice as much energy as 1
  gram of carbs. 9 kcal /gram

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PROTEIN METABOLISM

• USAGESmake cell parts, enzymes, muscle fibers
• Broken down into 20 essential amino acids. Of the
  twenty 8 amino acids cannot be made by the body.
  (has to come from diet)
• Can be an energy source when carbohydrates and
  fats are not available. 4 kcal / gram

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ENERGY BALANCE IN THE BODY

• IDEALLY
• Energy input total energy output (heat
  workenergy storage)
• BASAL METABOLIC RATE- amount of heat produced
  by the body per unit of time under basal
  conditions (AT REST) about 60-72 Cal -production
  by the thyroid gland is probably most important
  factor
• TOTAL METABOLIC RATE- total amount of
  kilocalories the body must consume to fuel all
  activities Skeletal muscle activity can
  increase BMR by 15 or 20 times and keep these
  levels elevated for several hours.

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Factors influencing BMR

1. SURFACE AREA-
2. THYROXINE PRODUCTION- (hormone produced by
   thyroid gland)
3. AGE
4. STRONG EMOTIONS or INFECTIONS
5. GENDER

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CHOLESTEROL METABOLISM

• LOW-DENSITY LIPOPROTEINS (LDL)- bad
  transports cholesterol to the body cells for
  usage
• HIGH-DENSITY LIPOPROTEINS (HDL)- good
  transports cholesterol from the body cells to be
  eliminated
• (Need both types of cholesterol but in the proper
  ratio)

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BODY TEMPERATURE REGULATION- controlled by
hypothalamus of the brain

• 96-100 degrees Fahrenheit can be considered
  normal.
• 98.6 degrees is the considered world wide average
  body temperature
• HEAT PROMOTING MECHANISMS
• 1. VASOCONSTRICTION of blood vessels
• 2. SHIVERING- increases skeletal muscle
  activity
• -Frostbite and hypothermia can result

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WEIGHT MANAGEMENT

• TOTAL KCAL CONSUMED TMR (then body fat
  remains the same)
• TOTAL KCAL CONSUMED gt TMR (then energy is stored
  as fat)
• TOTAL KCAL CONSUMED lt TMR ( then fat is broken
  down for energy use)

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HEAT LOSS MECHANISMS

• 1. EVAPORATION OF PERSPIRATION
• EXPANSION OF BLOOD VESSELS- skin becomes flush
  and radiates out heat
• Heat exhaustion and heat stroke can result
• (FEVER- is caused by white blood cells releasing
  pyrogens which act on the hypothalamus to
  increase the body temperature. RESETS the core
  body temperature to a higher temperature-
  Vasoconstriction and shivering occurs to raise
  body temp. to help fight of infections.)