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Digestive System. Digestive Tract. Also called alimentary canal Hollow tube roughly 8 meters in length. Structure of the Wall. Lumen - hollow center of tube Mucosa - epithelial layer with mucous-secreting cells

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digestive tract
Digestive Tract
  • Also called alimentary canal
  • Hollow tube roughly 8 meters in length
structure of the wall
Structure of the Wall
  • Lumen - hollow center of tube
  • Mucosa - epithelial layer with mucous-secreting cells
  • Submucosa - connective tissue layer rich with blood vessels, lymphatic vessels, and nerves
  • Muscular layer - smooth muscle layer
    • Circular- adjust lumen diameter
    • Longitudinal- adjust tract length
  • Serosa - outermost layer; secretes serous fluid
types of digestion
Types of Digestion
  • Mechanical
    • Physical breakdown of food into smaller pieces
  • Chemical
    • Breakdown of food molecules into more simple molecules by enzymes
mouth
Mouth
  • Receives food
  • Pushes into the remaining digestive tract
  • Includes: lips, teeth, cheeks, tongue, and palate
  • Two cavities:
    • 1) Oral cavity
      • Space between palate and tongue
    • 2) Vestibule
      • Cavity between teeth and lips and cheeks
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cheek and lips
Cheek and Lips
  • Cheeks
    • Contain muscles used during chewing
    • Stratified squamous epithelial tissue inside
  • Lips
    • Highly mobile skeletal muscles rich in sensory receptors
    • Aid in sensing temperature and texture of food
tongue
Tongue
  • Functions:
    • Keeps food underneath teeth
    • Mixes food with saliva
    • Moves bolus to the back of the mouth during swallowing
  • Muscular structure covered with mucous membrane
  • Root is attached to hyoid bone
  • Attached to floor of mouth by frenulum
  • Papillae provide surface friction and contain taste buds
palate
Palate
  • Forms roof of oral cavity
  • Hard palate
    • Anterior portion
  • Soft palate
    • Posterior portion; includes uvula
  • Soft palate raises during swallowing to close off nasal cavity
tonsils
Tonsils
  • Masses of lymphatic tissue
  • Lingual
    • On the tongue
  • Pharyngeal
    • Posterior wall of pharynx; also called adenoids
  • Palatine
    • Back of mouth on either side of tongue; associated with palate
teeth
Teeth
  • Two sets:
    • 1) Primary - 20 teeth
      • Lost/shed, nonpermanent
    • 2) Secondary - 32 teeth
      • Permanent, come in after primary teeth are lost/shed
  • Function:
    • Begin mechanical digestion of food
anatomy of tooth
Anatomy of Tooth
  • Crown - section above gingiva (gum)
  • Root -section below gingiva
  • Enamel - outer covering on crown
  • Dentin - bone-like substance that fills most of the tooth
  • Pulp cavity - connective tissue that contains blood vessels and nerves
  • Root canal - tubular extension that brings blood vessel and nerve to the pulp cavity
  • Cementum and periodontal ligament - hold tooth in alveolar process of jaw bone
salivary glands
Salivary Glands
  • Functions:
    • Moistens food
    • Binds food together
    • Dissolves food (so it can be tasted)
    • Cleanses mouth and teeth
    • Begins digestion of carbohydrates
  • Two types of cells
    • 1) Serous cells
      • Secretes serous fluid with enzyme amylase
    • 2) Mucous cells
      • Secretes mucous
salivary glands cont
Salivary Glands (cont)
  • 3 Types:
    • 1) Parotid glands:
      • Largest glands; anterior and inferior to ear; secrete watery saliva rich in amylase
    • 2) Submandibular:
      • Located in floor of mouth just inside lower jaw
    • 3) Sublingual:
      • Smallest glands; inferior to tongue; secrete saliva in mucous concentration
pharynx

Squid

Pharynx
  • Cavity located posterior to oral cavity
  • Provides connection to larynx and esophagus
  • Three parts:
    • 1) Nasopharynx- upper potion connecting to nasal cavity
    • 2) Oropharynx- middle section posterior to palate
    • 3) Laryngopharynx- lower portion posterior to larynx opening; leads to esophagus
swallowing action

Swallowing

Swallowing Action
  • Bolus stimulates sensory receptors in pharyngeal opening
  • Soft palate raises- closes nasal cavity
  • Larynx elevates; epiglottis closes off larynx
  • Tongue presses against palate
  • Longitudinal muscle pull pharynx towards food
  • Muscles relax near esophagus to open the tube
  • Peristalsis moves food into esophagus
esophagus
Esophagus
  • Hollow collapsible tube
  • Move food from pharynx to stomach
  • Passes through diaphragm in opening called esophageal hiatus
  • When food reaches opening of stomach, lower esophageal sphincter opens

Neck

stomach
Stomach
  • J-shaped pouch in abdomen
    • Holds about 1 liter of food
  • Functions:
    • Mix food with gastric juices
    • Begin protein digestion
    • Responsible for limited absorption
    • Moves food into small intestine

Squid Continues

stomach cont
Stomach (cont)
  • Rugae
    • Thick folds of mucosa and submucosa allow for expansion of stomach wall
  • Regions of the stomach
    • Cardiac - portion near esophagus
    • Fundic - portion lateral to cardiac where stomach ballons
    • Body - main portion of stomach between cardiac and pyloric
    • Pyloric - portion near opening to duodenum
    • Pyloric Sphincter - thick muscle band controlling entrance into duodenum
gastric secretions
Gastric Secretions
  • Mucosa is studded with gastric pits
  • Gastric pits are the opening to gastric glands
  • Gastric glands have three types of secreting cells:
    • 1) Mucous cells - secrete mucous; helps prevent stomach from digesting itself
    • 2) Chief cells - secrete pepsinogen
    • 3) Parietal cells - secrete HCl and intrinsic factor
gastric secretions cont
Gastric secretions (cont)
  • As food enters stomach, mixing actions occur to breakdown food into chyme
  • Gastric juices are added
    • HCl creates acidic environment
      • Shortens (activates) pepsinogen and makes it pepsin
    • Helps with vitamin B12 absorption
gastric secretions cont1
Gastric secretions (cont)
  • Limited absorption of the following occur:
    • Water
    • Salts
    • Alcohol
    • Lipid-soluble drugs
  • Chyme is moved to pyloric sphincter and pushed through
control of gastric secretions
Control of Gastric Secretions
  • Digestion is controlled by medulla oblongata
  • Parasympathetic NS:
    • Increases gastric secretions
  • Sympathetic NS:
    • Decreases gastric secretions
  • Hormones:
    • Gastrin - stimulates production of gastric juices
    • Cholecystokinin - released when small intestine fills with food; decreases gastric motility
review quiz mouth stomach
Review QuizMouth->Stomach
  • Contains rugae(folds)?

2. Contains lower sphincter and opens to stomach?

3. Mixes food with gastric juices?

4. Provides connection to larynx and esophagus?

5. Begins mechanical digestion of food?

  • Stomach
  • Esophagus
  • Stomach
  • Pharynx
  • Teeth
pancreas
Pancreas
  • Has endocrine and exocrine function (Ch 11!)
  • Nestled in C-shaped curve of duodenum
  • Pancreatic acinar cells
    • Secrete pancreatic juices
    • Clustered around tubes that eventually empty into pancreatic duct
  • Pancreatic duct run the length of the pancreas
    • Empties the juice into the duodenum
  • Hepatopancreatic sphincter
    • Controls emptying
pancreatic enzymes
Pancreatic Enzymes
  • Carbohydrates:
    • Pancreatic amylase
      • Breaks polysaccharides into dissaccharides
  • Lipids:
    • Pancreatic lipase
      • Breaks fats into glycerol and fatty acids
  • Nucleic Acids:
    • Nucleases
      • Breaks nucleic acids into nucleotides
pancreatic enzymes cont
Pancreatic Enzymes (cont)
  • Protein:
    • 3 enzymes (break them down into amino acids)
      • Trypsin
      • Chymotrypsin
      • Carboxypeptidase
    • Stored in zymogen granules in inactive forms
      • Ex: Trypsin’s inactive form is trypsinogen and is activated by enterokinase which is secreted by mucosa of duodenum
control of pancreatic juices and enzymes
Control of Pancreatic Juices and Enzymes
  • Parasympathetic NS control:
    • Stimulate release of pancreatic juices
  • Acidic chyme:
    • Stimulates release of secretin into the bloodstream
    • Stimulates release of pancreatic juice high in bicarbonate ions
  • Chyme high in protein and fat
    • Stimulates release of cholecystokinin into bloodstream
    • Stimulates release of pancreatic juice high in digestive enzymes
liver
Liver
  • Functions:
    • Controlling carbohydrate metabolism
    • Lipid metabolism
    • Protein metabolism
    • Storage
    • Blood filtering
    • Detoxification
    • Secretion of bile
liver structure
Liver Structure
  • Connective tissue divides liver intolarger right lobe and smaller left lobe
  • Liver is further divided into lobules
  • Hepatic cells radiate around a central vein
  • Spaces between the hepatic cells are called hepatic sinusoids
liver structure cont
Liver Structure (cont)
  • Blood from digestive track enters sinusoids from hepatic portal vein
  • Kupffer cells
    • Large macrophages (filter out pathogens from sinusoids)
  • Hepatic cells
    • Take out excess nutrients
  • Blood enters central vein and continues on its path back to the heart
what is bile
What is Bile?
  • Yellowish-green liquid secreted by liver cells
  • Includes:
    • Bile salts, bile pigments, cholesterol, and electrolytes
what does bile do
What does bile do?
  • Emulsification
    • Breaks fats globules into smaller droplets
    • Smaller droplets are easier for lipases to digest
  • Enhances absorption of fatty acids, cholesterol, and fat-soluble vitamins A, D, E, and K
bile cont
Bile (cont)
  • Sequence of travel:
    • Hepatic cells → Bile canaliculi → Bile Ductules → Bile duct → Hepatic duct → Common hepatic duct → Hepatopancreatic sphincter → Duodenum
gallbladder
Gallbladder
  • Between meals, bile up in common hepatic duct and into the cystic duct that attaches to it
  • Bile is backed up into gallbladder that is attached to the cystic duct
  • Gallbladder also absorbs excess water in bile therefore concentrating it
control of bile release
Control of Bile Release
  • Chyme high in protein and fat
    • Stimulates release of cholecystokinin into bloodstream which stimulates release of bile
  • Where peristalsis reaches hepatopancreatic sphincter, it relaxes and bile squirts into duodenum
small intestine structure
Small Intestine Structure
  • Three parts:
    • 1) Duodenum
      • First part after stomach; forms a C-shape
    • 2) Jejunum
      • More active than ileum
    • 3) Ileum
      • Leads to large intestine
small intestine structure cont
Small Intestine Structure (cont)
  • Mesentary
    • Holds loops of intestine to posterior abdominal wall
    • Supports blood vessels, lymphatic vessels, and nerves associated with intestine
  • Greater omentum
    • Double fold of membrane covering intestines
    • Helps wall off infected area
    • Prevent spread throughout cavity
structure of intestinal wall
Structure of Intestinal Wall
  • Wall has many projections called villi
    • Increase digestive surface area
    • Most numerous in duodenum and first part of jejunum
    • Covered with simple columnar epithelium
    • Have a connective tissue core
    • Contains blood vessels, a lymphatic vessel called a lacteal, and nerves
    • At the base are pockets called intestinal glands
small intestine secretions
Small Intestine Secretions
  • Mucosa
    • Goblet cells secrete mucos
  • Mucous
    • Secreting cell in submucosa - secrete alkaline mucous
  • Intestinal gland
    • Secrete watery substance
  • Epithelial cells of mucosa (all release enzymes)
    • Peptidase
    • Sucrase, maltase, and lactase
    • Intestinal lipase
control of small intestine secretions
Control of Small Intestine Secretions
  • Parasympathetic NS:
    • Triggers release when intestine wall is expanded
  • Other glands are stimulated by chyme (both mechanically and chemically)
sm intes absorption
Sm. Intes. Absorption
  • Small intestines = 95% of absorption of nutrients
  • Absorption follows release of chemicals:
    • Chemicals mix with chyme to help digestion and absorption
      • Bile
      • Pancreatic juices
      • Intestinal enzymes (maltase, lactase, sucrase, trypsin and chymotrypsin)
absorption cont
Absorption (cont)
  • Carbohydrates:
    • Simple sugars are moved into the blood stream by diffusion or active transport
  • Proteins:
    • Amino acids are actively transported into the blood stream
  • Lipids
    • Fatty acids and glycerol diffuse into cell of villi
    • Fatty acids with short chains diffuse into blood stream
    • Other are synthesized into fats and packed with protein (chylomicron) by the ER
    • These enter the lacteal and are carried to the blood
movements of sm intes
Movements of SmIntes
  • Mixing movements
    • Contractions move chyme from side to side to mix it
  • Peristalsis
    • Movement toward large intestine; very slow
  • Paristaltic rush
    • Forceful contraction if intestine if irritated or overdistended; pushes chyme to large intestine without much absorption’ leads to diarrhea
  • Ileocecal sphincter
    • Controls movement between ileum and cecum; normally closed; open after a meal
structure of large intestine
Structure of Large Intestine
  • Large diameter lumen
  • Composed of:
    • Cecum
    • Ascending colon
    • Transverse colon
    • Descending colon
    • Sigmoid colon
    • Rectum
    • Anal Canal
structure of large intestine wall
Structure of Large Intestine Wall
  • Longitudinal muscle occurs in three bands called teniae coli
  • Tension in teniae coli creates pouches called haustra in intestine
functions of large intestine
Functions of Large Intestine
  • Mucous secretion
    • Protects walls
    • Bind fecal matter
    • Controls pH
  • Absorption
    • Absorb water and electrolytes in proximal portion
  • Habitat for bacteria
    • Bacteria digest parts of fecal matter that is indigestible to us;
    • Synthesize vitamins that are then absorbed
movements of large intestine
Movements of Large Intestine
  • Mixing movements
    • Same as small intestine
  • Peristalsis
    • Waves occur only a few time a day; usually after meals
  • Defecation reflex
    • Feces are forced into rectum; internal anal sphincter is relaxed
  • Pressure is increased in abdomen which squeezes the rectum
  • External anal sphincter is relaxed
composition of feces
Composition of Feces
  • Water
  • Undigested material
  • Electrolytes
  • Mucous
  • Intestinal Cells
  • Bacteria

The Science of Farting

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Thumbs up, Thumbs Down
  • The large intestines houses bacteria such as E coli?

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2. The liver can absorb excess water in bile.

Thumbs down! Gallbladder

3. The small intestines contains mesentery which helps bind and support.

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4. The large intestines helps perform peristalsis and peristaltic rush.

Thumbs down! Small intestines

5. The liver metabolizes proteins and lipids and filters blood.

Thumbs up!!

digestive nutrients
Digestive Nutrients
  • Macronutrients
    • Carbohydrates
    • Protein
    • Lipids
  • Micronutrients
    • Vitamins
    • Minerals
  • Essential Nutrients
    • Nutrients that body cannot produce itself
carbohydrates
Carbohydrates
  • Process of Digestion:
    • Complex carbohydrate (Polysaccharide) → Disaccharide → Monosaccharide
  • Indigestible carbohydrates:
    • Ex: Cellulose - provides roughage (or fiber) to diet
carbohydrates cont
Carbohydrates (cont)
  • Fructose and galactose are converted to glucose by the liver
  • Excess glucose
    • Liver converts glucose to glycogen or to fats
  • Deficiency of Glucose
    • Liver converts glycogen, fats, or proteins to glucose
  • Requirements for carbohydrates varies depending upon energy expenditures
    • More energy = more carbohydrate requirement
    • Ex: Athletes will consume pasta before event for more energy
lipids
Lipids
  • Process of Digestion:
    • Fat → Glycerol + Fatty Acids
  • Use of Lipid Products:
    • Used to synthesize glucose
    • Converted to acetyl CoA and enters Krebs/Citric acid cycle (of cellular respiration)
    • Stored in adipose tissue (insulation)
    • Used in building cellular structures (cell and organelle membranes)
    • Used to synthesize some hormones (steroid)
    • Animation
protein
Protein
  • Process of Digestion:
    • Polypeptide → Amino Acids
  • Uses of Amino Acids:
    • Used to create enzymes
    • Used to create structural proteins (muscle, etc)
    • Various other uses
    • Deaminated (removal of amine group from amino acid) by liver
      • Converted into products used in citric acid cycle (cellular respiration)
proteins cont
Proteins (cont)
  • Nonessential amino acids
    • Can be synthesized by body; do not need to be in diet
  • Essential amino acids
    • Cannot be synthesized by body; do need to be in diet
  • Complete proteins
    • Dietary proteins that contain enough of the essential amino acids
  • Incomplete proteins
    • Dietary proteins that don’t contain enough of the essential amino acids
  • Partially complete proteins
    • Contain enough essential proteins to sustain life but not enough to promote growth
vitamins
Vitamins
  • Organic compounds requires in small amounts for normal metabolism
  • Fat-soluble: A, D, E, and K
    • Accumulate in tissues and can lead to overdoses
  • Water-soluble: B and C
    • Excess is often excreted
minerals
Minerals
  • Elements other than carbon needed for human metabolism
  • Concentrated in bones and teeth; parts of structural components and enzymes; free-floating ions
  • Major Minerals: Ca, P, K, S, Na, Cl, and Mg
  • Trace Elements: Fe, Mn, Cu, I, Co, Zn, F, Cr
diseases and disorders
Diseases and disorders
  • Hepatitis:
    • Inflammation of liver
    • Caused by class of viruses (usually)
      • Names of hepatitis (A-G) come from virus
    • Symptoms:
      • Lack of appetite
      • Nausea and vomiting
      • Low fever and mild headache
      • Stiff joints and rash
      • Upper right quadrant pain in abdomen
      • Dark/foamy urine
      • Yellowish skin/sclera of eye
diseases and disorders1
Diseases and disorders
  • Lactose Intolerance:
    • Lactose sugar unable to be broken down
    • Caused by lack of production of lactase (enzyme which breaks down lactose)
    • Symptoms:
      • Bloating
      • Intestinal cramps
      • Diarrhea
    • Avoidance:
      • Avoid lactose sugar (drink soy/almond milk)
      • Take lactase pills before eating lactose