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Digestive System Gissel Hernandez per. 5 - Coggle Diagram
Digestive System
Gissel Hernandez
per. 5
Major Organs of the Digestive
System
• Teeth lie in sockets in gum-covered margins of mandible and maxilla
• Mastication: process of chewing that tears and grinds food into smaller fragments
• Dentition and the dental formula
– Primary dentition consists of 20 deciduous teeth, or milk or baby teeth, that erupt
between 6 and 24 months of age
– 32 deep-lying permanent teeth enlarge and develop while roots of milk teeth are
resorbed from below, causing them to loosen and fall out (~ 6–12 years of age)
Salivary Glands
• Functions of saliva
– Cleanses mouth
– Dissolves food chemicals for taste
– Moistens food; compacts into bolus
– Begins breakdown of starch with enzyme amylase
Mouth
• Also called the oral (buccal) cavity
– Oral orifice is the anterior opening
– Walls of mouth lined with stratified squamous epithelium
• Lips and cheeks
– Lips (labia): composed of fleshy orbicularis oris muscle
– Cheeks: composed of buccinator muscles
– Labial frenulum: median attachment of each lip to gum
• Palate
– Palate forms the roof of the mouth and has two distinct parts
Hard palate: formed by palatine bones and palatine processes of maxillae
with a midline ridge called raphe
Soft palate: fold formed mostly of skeletal muscle
– Closes off nasopharynx during swallowing
– Uvula: fingerlike projection that faces downward from free edge of soft
palate
Tongue
• Tongue occupies floor of mouth
• Functions include:
– Gripping, repositioning, and mixing of food during chewing
– Formation of bolus, mixture of food and saliva
– Initiation of swallowing, speech, and taste
• Lingual frenulum: attachment to floor of mouth
Major Functions of the
Digestive System
• Organs of the digestive system fall into two groups:
Alimentary canal (gastrointestinal or GI tract or gut)
▪ Continuous muscular tube that runs from the mouth to anus
▪ Digests food: breaks down into smaller fragments
▪ Absorbs fragments through lining into blood
▪ Organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus
Accessory digestive organs
▪ Teeth
▪ Tongue
▪ Gallbladder
▪ Digestive glands: produce secretions that help break down foodstuffs
– Salivary glands
– Liver
– Pancreas
• Processing of food involves six essential activities:
Ingestion: eating
Propulsion: movement of food through the alimentary canal, which includes:
▪ Swallowing
▪ Peristalsis: major means of propulsion of food that involves alternating waves of contraction and relaxation
Mechanical breakdown: includes chewing, mixing food with saliva, churning food in stomach, and segmentation
▪ Segmentation: local constriction of intestine that mixes food with digestive juices
Digestion: series of catabolic steps that involves enzymes that break down complex food molecules into chemical building blocks
Absorption: passage of digested fragments from lumen of GI tract into blood or lymph
Defecation: elimination of indigestible substances via anus in form of feces
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• Main functions of the digestive system
– Take in food
– Break it down into nutrient molecules
– Absorb molecules into the bloodstream
– Rid body of any indigestible remains
Major Functions of
Urinary System
Kidneys are part of the urinary system, which also includes:
– Ureters: transport urine from kidneys to urinary bladder
– Urinary bladder: temporary storage reservoir for urine
– Urethra: transports urine out of body
• Kidneys, a major excretory organ, maintain the body’s internal environment by:
– Regulating total water volume and total solute concentration in water
– Regulating ion concentrations in extracellular fluid (ECF)
– Ensuring long-term acid-base balance
– Excreting metabolic wastes, toxins, drugs
– Producing erythropoietin (regulates blood pressure and renin (regulates RBC production)
– Activating vitamin D
– Carrying out gluconeogenesis, if needed
Digestive Enzymes
• Large intestine has three unique features not seen elsewhere:
– Teniae coli: three bands of longitudinal smooth muscle in muscularis
– Haustra: pocketlike sacs caused by tone of teniae coli
– Epiploic appendages: fat-filled pouches of visceral peritoneum
• Ileocecal valve control
– Ileocecal sphincter relaxes and admits chyme into large intestine when:
▪ Gastroileal reflex enhances force of segmentation in ileum
▪ Gastrin increases motility of ileum
– Ileocecal valve flaps close when chyme exerts backward pressure
▪ Prevents regurgitation into ileum
Nephron Anatomy and Physiology
• Nephrons are the structural and functional units that forms urine in the Kidneys
• > 1 million per kidney
• Two main parts
– Renal corpuscle
– Renal tubule
Proximal convoluted tubule (PCT)
– Cuboidal cells with dense microvilli that form brush border
▪ Increase surface area
▪ Also have large mitochondria
– Functions in reabsorption and secretion
– Confined to cortex
Nephron loop
– Formerly called loop of Henle
– U-shaped structure consisting of two limbs
▪ Descending limb
– Proximal part of descending limb is continuous with proximal tubule
– Distal portion also called descending thin limb; simple squamous epithelium
▪ Ascending limb
– Thick ascending limb
• Thin in some nephrons
– Cuboidal or columnar cells
Layers of GI Tract
• Organs of the digestive system fall into two groups:
Alimentary canal (gastrointestinal or GI tract or gut)
▪ Continuous muscular tube that runs from the mouth to anus
▪ Digests food: breaks down into smaller fragments
▪ Absorbs fragments through lining into blood
▪ Organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine,
anus
Mucosa
– Tunic layer that lines lumen
– Functions: different layers perform one or all three
▪ Secretes mucus, digestive enzymes, and hormones
▪ Absorbs end products of digestion
▪ Protects against infectious disease
Submucosa
– Consists of areolar connective tissue
– Contains blood and lymphatic vessels, lymphoid follicles, and submucosal nerve
plexus that supply surrounding GI tract tissues
– Has abundant amount of elastic tissues that help organs to regain shape after storing
large meal
Muscularis externa
– Muscle layer responsible for segmentation and peristalsis
– Contains inner circular muscle layer and outer longitudinal layers
▪ Circular layer thickens in some areas to form sphincters
Serosa
– Outermost layer, which is made up of the visceral peritoneum
Location of Digestion and Absorption
of Macromolecule
• Vitamin absorption
– In small intestine
▪ Fat-soluble vitamins (A, D, E, and K) are carried by micelles; diffuse into
absorptive cells
▪ Water-soluble vitamins (C and B) are absorbed by diffusion or by passive or
active transporters
▪ Vitamin B12 (large, charged molecule) binds with intrinsic factor and is absorbed
by endocytosis
– In large intestine: vitamin K and B vitamins from bacterial metabolism are absorbed
• Absorption of electrolytes
– Most ions are transported actively along length of small intestine
– Iron and calcium are absorbed in duodenum
– 𝑁𝑎+ absorption is coupled with active absorption of glucose and amino acids
– 𝐶𝑙− is transported actively
– 𝐾+ diffuses in response to osmotic gradients; lost if water absorption is poor
– Usually amount in intestine is amount absorbed
Absorption of water
– 9 L water, most from GI tract secretions, enter small intestine
▪ 95% is absorbed in the small intestine by osmosis
▪ Most of rest is absorbed in large intestine
– Net osmosis occurs if concentration gradient is established by active transport of
solutes
– Water uptake is coupled with solute uptake
Disorders of the Digestive
and Urinary Systems
Peptic Ulcers: Sores that develop in the lining of the stomach or the duodenum
Colon Disease: Colo rectal cancer uncontrolled cell growth in the colon
Inflammatory Bowel Disease: A chronic complex intestinal condition that causes inflammation in the digestive tract including Crohn's disease
Bladder Cancer: The bladder wall has many layers made up of different types of cells when cells of bladder grow abnormally become BC
Gastroesphageal Reflux Diseas: A chronic diseas that occurs when the esopageal sphincter relaxes, allowing the conents of the stomach to move back into the esophagus
Urinary Tract Infection: The abnormal growth of bacteria anywhere along the urinary tract
Cholecytisis: An inflammation of the gallbladder
Kidney Stones: When the urine has high levels of minerals and salts, hard stones can form
Major Organs of the Urinary System
• Kidneys are part of the urinary system, which also includes:
– Ureters: transport urine from kidneys to urinary bladder
– Urinary bladder: temporary storage reservoir for urine
– Urethra: transports urine out of body
• Kidneys, a major excretory organ, maintain the body’s internal environment by:
– Regulating total water volume and total solute concentration in water
– Regulating ion concentrations in extracellular fluid (ECF)
– Ensuring long-term acid-base balance
– Excreting metabolic wastes, toxins, drugs
– Producing erythropoietin (regulates blood pressure and renin (regulates RBC production)
– Activating vitamin D
– Carrying out gluconeogenesis, if needed