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A&P ch. 16, 23, 24

endocrine, digestive, and nutrition systems

Mesentary a double layer of peritoneum Routes for blood vessels, lymphatics, and nerves Holds organs in place and stores fat
Retroperitoneal organs lie posterior to the peritoneum
Intraperitoneal (peritoneal) organs are surrounded by the peritoneum
Peritoneum serous membrane of the abdominal cavity (2 layers) Visceral peritoneum Parietal peritoneum
Visceral peritoneum on external surface of most digestive organs
Parietal peritoneum lines the body wall
Peritoneal cavity Between the two peritoneums Fluid lubricates mobile organs
The alimentary canal or gastrointestinal (GI) tract digests and absorbs food 2 parts: Alimentary canal Accessory digestive organs
Alimentary canal mouth, pharynx, esophagus, stomach, small intestine, and large intestine
Accessory digestive organs teeth, tongue, gallbladder, salivary glands, liver, and pancreas
Arteries Hepatic, splenic, and left gastric Inferior and superior mesenteric
Hepatic portal circulation Drains nutrient-rich blood from digestive organs Delivers it to the liver for processing
Histology of the Alimentary Canal 4 layers Mucosa (most inner) Submucosa Muscularis externa Serosa (most outer)
Mucosa Lines the lumen Three sublayers: epithelium, lamina propria muscularis mucosae
Functions of mucosa Secretes mucus, digestive enzymes and hormones Absorbs end products of digestion Protects against infectious disease
Muscularis mucosae (layer of mucosa) smooth muscle cells that produce local movements of mucosa
Lamina Propria (layer of mucosa) Loose areolar connective tissue
Simple columnar epithelium and mucus-secreting goblet cells (layer of mucosa) Stomach and small intestine mucosa contain: Enzyme-secreting cells Hormone-secreting cells
submucosa dense connective tissue, blood and lymphatic vessels, lymph nodes, and nerves
Muscularis externa responsible for segmentation and peristalsis (movement of GIT) inner: circular outer: longitudinal
serosa the protective visceral peritoneum Replaced by the fibrous adventitia in the esophagus Retroperitoneal organs have both an adventitia and serosa
Sympathetic impulses inhibit secretion and motility
Parasympathetic impulses stimulate (motility and secretion)
Myenteric nerve plexus Controls GI tract motility
Submucosal nerve plexus Regulates glands and smooth muscle in the mucosa
Intrinsic nerve supply of the alimentary canal Submucosal nerve plexus Myenteric nerve plexus
retroperiteneal organs duodenum pancreas ascending colon descending colon
difference between colon and large intestine colon is a part of the large intestine
stratified squamous epithelium in the digestive tract mouth pharynx esophagus anus
teeth Primary and permanent dentitions are formed by age 21 20 deciduous teeth erupt (6–24 months of age) 32 permanent teeth
permanent teeth 32 All except third molars erupt by the end of adolescence
deciduous teeth 20 Roots are resorbed, teeth fall out (6–12 years of age) as permanent teeth develop
Tooth structure crown root cementum periodontal ligament dentin pulp cavity pulp root canal
crown the exposed part above the gingiva (gum) Covered by enamel: the hardest substance in the body (calcium)
root portion embedded in the jawbone Connected to crown by neck
cementum calcified connective tissue Covers root and attaches it to the periodontal ligament
periodontal ligament Forms fibrous joint called a gomphosis
dentin bonelike material under enamel maintained by osteoblasts
pulp cavity cavity surrounded by dentin
pulp connective tissue, blood vessels, and nerves
root canal extends from pulp cavity to the apical foramen of the root
Salivary glands Parotid gland Submandibular gland Sublingual gland
Parotid gland Anterior to the ear external to the masseter muscle Parotid duct opens into the vestibule next to second upper molar
Submandibular gland Medial to the body of the mandible Duct opens at the base of the linguinal frenulum
Sublingual gland Anterior to the submandibular gland under the tongue Opens ducts
Pharynx Oropharynx and laryngopharynx Allow passage of food, fluids, and air Stratified squamous epithelium lining skeletal muscle layers: inner longitudinal, outer pharyngeal constrictors
Esophagus Flat muscular tube from laryngopharynx to stomach Esophageal mucosa contains stratified squamous epithelium Changes to simple columnar at the stomach Esophageal glands in submucosa secrete mucus to aid in bolus movement
Where does the esophagus pierce the diaphragm? esophageal hiatus
Where does the esophagus join the stomach? at the cardiac orifice
Heartburn stomach acid regurgitating into esophagus First symptom of (GERD) Caused by excess food/drink, extreme obesity, pregnancy, running OR hiatal hernia: (part of stomach protrudes above diaphragm) lead to issues with esophagus
Gross anatomy of stomach Cardiac region (cardia) Fundus Body Pyloric region Greater curvature Lesser omentum Greater omentum
Greater curvature Convex lateral surface
Lesser curvature Concave medial surface
Lesser omentum From the liver to the lesser curvature
Greater omentum Drapes from greater curvature Anterior to the small intestine
Cardiac region (cardia) Surrounds the cardiac orifice
Fundus Dome-shaped region beneath the diaphragm
body midportion
Pyloric region antrum, pyloric canal, and pylorus Pylorus is continuous with the duodenum through the pyloric valve (sphincter)
ANS nerve supply Sympathetic via splanchnic nerves and celiac plexus Parasympathetic via vagus nerve
Blood supply Celiac trunk Veins of the hepatic portal system
cell types in gastric gland Mucous neck cells Parietal cells Chief cells Enteroendocrine cells
Mucous trunk secrete thin, acidic mucus
Parietal cells secrete HCl and Intrinsic factor
Chief cells secrete pepsinogen
Enteroendocrine cells hormones - gastrin
Small intestine subdivisions Duodenum Jejunum Illeum (attached posteriorly by mesentery)
duodenum retroperitoneal
Jejunum attached posteriorly by mesentery
Illeum attached posteriorly by mesentery
Small intestine Major organ of digestion and absorption 2–4 m long; from pyloric sphincter to ileocecal valve
Duodenum The bile duct and main pancreatic duct Join at the hepatopancreatic ampulla Enter the duodenum at the major duodenal papilla Are controlled by the hepatopancreatic sphincter
Circular folds (Modification) Permanent (~1 cm deep) Force chyme to slowly spiral through lumen
Structural modifications Increase surface area of proximal part for nutrient absorption Circular folds (plicae circulares) Villi Microvilli
Villi Motile fingerlike extensions (~1 mm high) of the mucosa Villus epithelium Simple columnar absorptive cells (enterocytes) Goblet cells
Microvilli Projections (brush border) of absorptive cells Bear brush border enzymes
Liver associated structures Lesser omentum anchors liver to stomach Hepatic artery and vein at the porta hepatis Bile ducts
Bile ducts Common hepatic duct leaves the liver Cystic duct connects to gallbladder Bile duct formed by the union of the above two ducts
Liver lobules Hexagonal structural and functional units Filter and process nutrient-rich blood Composed of plates of hepatocytes (liver cells) Longitudinal central
Gallbladder Thin-walled muscular sac on the ventral surface of the liver Stores and concentrates bile by absorbing its water and ions Releases bile via the cystic duct, which flows into the bile duct
Pancreas location Location Mostly retroperitoneal, deep to the greater curvature of the stomach Head is encircled by the duodenum; tail abuts the spleen
Pancreas endocrine function Pancreatic islets secrete insulin and glucagon
Pancreas exocrine function Acini (clusters of secretory cells) secrete pancreatic juice granules of secretory cells contain digestive enzymes
Large intestine features Teniae coli Haustra Epiploic appendages
Teniae coli Three bands of longitudinal smooth muscle in the muscularis
Haustra Pocketlike sacs caused by the tone of the teniae coli
Epiploic appendages Fat-filled pouches of visceral peritoneum
Large intestine regions Cecum (pouch with attached vermiform appendix) Colon Rectum Anal canal
which parts of the large intestine are retroperitoneal? Ascending colon and descending colon are retroperitoneal
Function of mesocolons? Transverse colon and sigmoid colon are anchored via mesocolons (mesenteries)
Rectum Three rectal valves stop feces from being passed with gas
Anal cavity The last segment of the large intestine
Sphincters Internal anal sphincter—smooth muscle External anal sphincter—skeletal muscle
Large intestine microscopic anatomy Mucosa of simple columnar epithelium except in the anal canal (stratified squamous) Abundant deep crypts with goblet cells Superficial venous plexuses of the anal canal form hemorrhoids if inflamed
Digestive process essential activities ingestion Propulsion & mechanical digestion Chemical digestion absorption defecation
Digestive process The GI tract is a “assembly” line Nutrients become more available to the body in each step
Enteric nervous system Short relexes Long reflexes
Short relexes mediated by enteric nerve plexuses (gut brain); respond to stimuli in GI tract
Long reflexes respond to stimuli arising inside or outside of gut, such as from autonomic nervous system Parasympathetic system enhances digestive process Sympathetic system inhibits digestion
Mucosa main site of nutrient absorption
mesentery Omenta is the special name for part of the mesentery. It holds the organs of the abdomen in place. It provides a route for blood vessels, lymphatics, and nerves to reach the digestive viscera
Muscularis externa Responsible for segmentation and peristalsis
accessory organs of the digestive system? teeth tongue salivary glands
the major means of propulsion in the digestive system Peristalsis
serosa Protective outermost layer of the alimentary canal
Chemical digestion. Enzymatic degradation of foodstuffs into simpler molecules
layers of the wall of the GI tract Mucosa, submucosa, muscularis externa, serosa
The short reflexes in the digestive system are mediated by the enteric nerve plexuses
absorption Passage of digested materials from the lumen of the GI tract into the blood or lymph
visceral peritoneum serous membrane that covers the external surface of most digestive organs is called the
which cells produce HCI parietal cells
activation of pancreatic proteases occurs in the __________. duodenum
Pepsin enzymatically digests protein
intestinal phase of gastric regulation the stomach is initially stimulated and later inhibited
found in pancreatic secretions Bicarbonate ions Procarboxypeptidase Chymotrypsinogen
characteristics of the liver It is highly regenerative. It stores glucose as glycogen. It has a role in detoxifying the blood.
gastrin Stimulated by partially digested proteins in the stomach and increases gastric gland secretions
CCK Increases the secretions of enzyme-rich pancreatic juice
What is the main organic molecule digested in the stomach? proteins
What substances from different organs would mix together at the hepatopancreatic ampulla? Bile and pancreatic enzymes
Some aspects of the __________ phase of gastric secretion may be considered conditioned reflexes. cephalic
Which of the following products does the stomach produce? HCI and intrinsic factor
Digestion of carbohydrates and proteins by brush border enzymes occurs within the __________ of the small intestine. microvilli
The only stomach function that is essential to life is __________. the secretion of intrinsic factor
Functions of saliva Cleanses mouth Dissolves food chemicals for taste Moistens food; compacts into bolus Begins breakdown of starch with enzyme amylase
mechanical digestion food is "chopped up" with teeth
Peristalsis adjacent segments of the ailmentary canal organs alternately contract and relax (food is moved distally) little mixing, mostly for propulsion
Segmentation nonadjacent segments of the ailmentary canal contract and relax (food is moved forward then backwards) mostly mixing, little propulsion
Enteric Nervous System (the two reflexes it participates in) Short reflexes Long reflexes
Short reflexes mediated by enteric nerve plexuses (gut brain); respond to stimuli in GI tract
Long reflexes respond to stimuli arising inside or outside of gut, such as from autonomic nervous system Parasympathetic system enhances digestive process Sympathetic system inhibits digestion
regulating digestive activity Mechanical and chemical stimuli Effectors Neurons
Effectors smooth muscle and glands
Neurons intrinsic and extrinsic) and hormones and glands
What do Mechanoreceptors and chemoreceptors respond to? stretch changes in osmolarity Changes in pH presence of substrate and end products of digestion
The GI tract initiates reflexes that activate or inhibit digestive glands and stimulate smooth muscle to mix and move lumen contents true
Salivary glands composed of 2 types of secretory cells Serous cells Mucous cells
Serous cells produce watery secretion, enzymes, ions, bit of mucin
mucous cells produce mucous
Composition of saliva 97–99.5% water, slightly acidic solution containing Electrolytes—Na+, K+, Cl–, PO4 2–, HCO3– Salivary amylase Mucin
Extrinsic salivation Ingested food - stimulates chemoreceptors and mechanoreceptors in the mouth Salivatory nuclei in the brain stem - impulses along parasympathetic fibers in cranial nerves VII and IX
Sympathetic nervous system stimulation inhibits salivation and causes dry mouth
Mouth Ingestion Mechanical digestion Mastication is partly voluntary, partly reflexive Chemical digestion (salivary amylase) Swallowing Deglutition (swallowing)
Deglutition Involves the tongue, soft palate, pharynx, esophagus, and 22 muscle groups
Deglutition phases Pharyngeal-esophageal phase Buccal phase
Buccal phase Voluntary contraction of the tongue
Pharyngeal-esophageal phase Involuntary Control center in the medulla and lower pons
Bolus saliva mixed partially digested food which is swallowed
Stomach Holds ingested food Degrades this food both physically and chemically Delivers chyme to the small intestine Enzymatically digests proteins with pepsin Secretes intrinsic factor factor required for absorption of vitamin B12
Gastric Gland Secretion types Mucous nek cells Parietal cell secretions Chief secretions
Mucous nek cells thin, acidic mucous
Parietal cell secretions HCl Intrinsic factor required for absorption of vitamin B12 in small intestine
Chief secretions Pepsinogen - inactive enzyme Activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism)
Enteroendocrine cells Secrete chemical messengers into the lamina propria Paracrines Serotonin and histamine Hormones Somatostatin and gastrin
Mucosal barriers Mucosal barrier protects stomach and is created by three factors Thick layer of bicarbonate-rich mucus Tight junctions between epithelial cells
Gastritis Inflammation caused by anything that breaches stomach’s mucosal barrier
Peptic or gastric ulcers Can cause erosions in stomach wall Most ulcers caused by bacterum Helicobacter pylori Can also be caused by non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin
Digestive processes in the stomach Carries out breaking down of food Serves as holding area for food Delivers chyme to small intestine Denatures proteins by HCI
pepsin carries out enzymatic digestion of proteins
what is the only necessary function of the stomach for survival? secretion of intrinsic factor for vitamin B12 absorption
Neural mechanisms Vagus nerve stimulation increases secretion Sympathetic stimulation decreases secretion
Hormonal mechanisms Gastrin stimulates enzyme and HCI secretion Gastrin antagonists are secreted by small intestine
phases of gastric secretion Cephalic (reflex) phase Gastric phase Intestinal phase
Cephalic phase (reflex phase) few minutes prior to food entry thought, sight, smell, taste of food
Gastric phase 3–4 hours after food enters the stomach
Intestinal phase brief stimulatory effect as partially digested food enters the duodenum, followed by inhibitory effects (enterogastric reflex and enterogastrones)
where is Gastric Contractile Activity most vigorous? pylorus
Chyme Delivered in about 3 ml spurts to the duodenum, or Forced backward into the stomach
Vomiting (emesis) Extreme stretching Intestinal irritants, such as bacterial toxins, excessive alcohol, spicy food, certain drugs
Intestinal juice Secreted in response to distension or irritation of the mucosa Slightly alkaline and isotonic with blood plasma Largely water, enzyme-poor, but contains mucus Facilitates transport and absorption of nutrients
Bile Yellow-green, alkaline solution containing
bile salts cholesterol derivatives that function in fat emulsification and absorption
Bilirubin: pigment formed from heme
Enterohepatic circulation Recycles bile salts Bile salts  duodenum  reabsorbed from ileum  hepatic portal blood -> liver -> secreted into bile
Protease activation in duodenum Trypsinogen is activated to trypsin by brush border enzyme enteropeptidase Procarboxypeptidase and chymotrypsinogen are activated by trypsin
Bile secretion is stimulated by... Bile salts in enterohepatic circulation Secretin from intestinal cells exposed to HCl and fatty chyme
Gallbladder contraction is stimulated by... Cholecystokinin (CCK) from intestinal cells exposed to proteins and fat in chyme Vagal stimulation (minor stimulus)
major nutrients lipids, carbs, protein
Food groups represented on MyPlate dairy grains fruits vegetables
Monosaccharide & disaccharides Sugars (mono- and disaccharides) in fruits, sugarcane, sugar beets, honey, and milk
Polysaccharides insoluble fibers soluble fibers
insoluble fiber cellulose in vegetables provides roughage
soluble fiber pectin in apples and citrus fruits reduces blood cholesterol levels
What role does excess glucose play? converted to glycogen or fat, then stored
Glucose Glucose: fuel most used by cells to make ATP Some cells use fat for energy Neurons and RBCs rely entirely on glucose Neurons die quickly without glucose
Carbohydrates daily dosage 45-65% of caloric intake should be mostly complex carbohydrates (whoke grains and vegetables)
Triglycerides most abundant form Found in saturated fats in meat, dairy foods, tropical oils, or hydrogenated oils Unsaturated fats found in seeds, nuts, olive oil, and most vegetable oils
Cholesterol found in egg yolk, meats, organ meats, shellfish, and milk products Liver makes ~85% cholesterol
Essential fatty acids linoleic and linolenic acid found in most oils - must be eaten
Role of lipids: Adipose tissue protection, insulation, fuel storage
Role of lipids: Phospholipids essential in myelin sheaths and cell membranes
Role of lipids: Cholesterol stabilizes membranes; precursor of bile salts, steroid hormones
Role of lipids: Prostaglandins - smooth muscle contraction, BP control, inflammation
other roles of lipids Help absorb fat-soluble vitamins Major fuel of hepatocytes and skeletal muscle
Dietary recommendations: lipids American Heart Association recommendations Fats: 30% or less of total caloric intake Saturated fats: 10% or less of total fat intake Cholesterol: no more than 300 mg/day (about 1-1/2 egg yolks)
Types of proteins complete proteins incomplete proteins
complete proteins Animal products (eggs, milk, fish, most meats), soybeans, Contain all needed essential amino acids
incomplete proteins Legumes, nuts, and cereals contain (lack some essential amino acids)
Uses of protein in the body Structural materials: makes cell membrane Functional molecules Nitrogen balance
Nitrogen balance Homeostatic state: protein synthesis = rate of breakdown and loss (+) balance: synthesis exceeds breakdown (children, pregnant women, tissue repair) (-) balance: breakdown > synthesis (ex: stress, burns, infection, injury, poor dietary proteins)
daily diet breakdown: carbs: 45-65% protein: 10-20% lipids: less than 30%
role of vitamins organic compounds that function as coenzymes most must be ingested except vitamin D, B, K, and beta carotene
types of vitamins water-soluble fat-soluble
Vitamin B deficiency beriberi
B12 deficiency anemia
folic acid deficiency spina bifida and anemia
vitamin C deficiency scurvy
vitamin A deficiency night blindness
vitamin D deficiency children: rickets adults: osteomalacia
vitamin K deficiency defective blood clotting
minerals Calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium
Anabolism synthesis of large molecules from small ones (example: triglycerides
Catabolism hydrolysis of complex structures to simpler ones
Metabolism sum of all biochemical reactions inside a cell involving nutrients
Cellular respiration catabolic breakdown of food fuels whereby energy from food is captured to form ATP in cells
Phosphorylation enzymes shift high-energy phosphate groups of ATP to other molecules Phosphorylated molecules become activated to perform cellular functions
How many stages are there to digesting nutrients? three stages
Stage one of digesting nutrients Digestion, absorption, and transport to tissues – GI tract
Stage two of digesting nutrients Cellular processing (in cytoplasm) – tissue cells Synthesis of lipids, proteins, and glycogen, or Catabolism (glycolysis) into pyruvic acid and acetyl CoA
Stage three of digesting nutrients Oxidative breakdown of intermediates into CO2, water, and ATP –mitochondria
Glucose catabolism reaction formula C6H12O6 + 6O2  6H2O + 6CO2 + 32 ATP + heat
three pathways to complete glucose catabolism Glycolysis Krebs cycle Electron transport chain and oxidative phosphorylation
Glycolysis Also called glycolytic pathway Anaerobic: occurs despite presence/absence of O2 Occurs in cytosol Glucose -> 2 pyruvic acid molecules ATP – net gain of 2 ATP
Krebs Cycle Also called Citric acid cycle Occurs in mitochondrial matrix Fueled by pyruvic acid and fatty acids pyruvic acid enters transitional phase pyruvic acid is converted to acetyl coenzyme A (acetyl CoA)
Glycogenesis formation of glycogen (glucose -> glycogen)
Glycogenolysis breakdown of glycogen (glycogen -> sugar)
Gluconeogenesis AA and FA -> glucose
Lipogenesis: making of fat
lipolysis breakdown of stored fats into glycerol and fatty acids; reverse of lipogenesis
What are fatty acids prefered by? liver, cardiac muscle, resting skeletal muscle for fuel
When does lipolysis occur? when carb intake is inadequate
amino acid degredation Transamination Oxidative deamination Keto acid modification
Transamination transfer their amine group and become glutamic acid
Oxidative deamination In liver, amine group is removed as ammonia (NH3)
Keto acid modification -Keto acids formation
Created by: davisobr



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