Anatomy Week 1 - assorted lecture notes PDF

Preview

Summary

assorted lecture notes...

Description

1080 Anatomy & Physiology

January 9th, 2018

Week 1 Anatomy & Physiology Gastrointestinal System – Chapter 24 Major Organs: -

Oral cavity (mouth): ingestion, mechanical digestion with teeth and tongue, moistening, mixing with salivary secretions. Pharynx: muscular propulsion of materials into esophagus. Esophagus: transport of materials to stomach. Stomach: chemical digestion of materials by acid and enzymes; mechanical digestion through muscular contractions. Small intestine: enzymatic digestion and absorption of water, organic substrates, vitamins, and ions. Large intestine: dehydration and compaction of indigestible materials in preparation for elimination.

Accessory Organs: -

Teeth: mechanical digestion by chewing. Tongue: assists mechanical digestion with teeth, sensory analysis. Salivary Glands: secretion of lubricating fluid containing enzymes that break down carbohydrates. Liver: secretion of bile (important for lipid digestion), storage of nutrients, many other vital functions. Gallbladder: storage and concentration of bile. Pancreas: exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones.

Gastrointestinal System 1. Ingestion; occurs when food enters oral cavity. 2. Mechanical digestion and propulsion; crushing and shearing of food, as well as propelling food along digestive tract. 3. Chemical digestion; chemical breakdown of food into small organic fragments for absorption by digestive epithelium. 4. Secretion; release of water, acids, enzymes, buffers, and salts. Secretion via epithelium of digestive tract, glandular organs, and gallbladder. 5. Absorption; movement of organic molecules, electrolyte, vitamins, minerals, and water across digestive epithelium and into interstitial fluid of digestive tract. 6. Defecation; elimination of wastes from body; compacted, dehydrated wastes are called feces.

January 9th, 2018

1080 Anatomy & Physiology Linings of Digestive tract: -

Safeguards surround tissues against: corrosive effects of digestive acids and enzymes, mechanical stress such as abrasion, and bacteria ingested with food or that reside in digestive tract.

Peritoneum: -

-

A lining of mesothelium and areolar tissue surrounding the abdominal cavity. Composed of the visceral layer (covering internal organs within the cavity a.k.a. serosa) and the parietal layer (surrounding the outer wall of the cavity). Visceral peritoneum (serosa) covers organs within peritoneal cavity. Parietal peritoneum lines inner surfaces of body wall.

Peritoneal Fluid: -

Produced by serous membrane lining Allows sliding of parietal and visceral surfaces without friction or irritation About 7 liters produced and absorbed daily, but very little in peritoneal cavity at one time. Ascites – a-SY-teez – abdominal swelling due to buildup of peritoneal fluid. Usually involves liver. Mesenteries: sheets of peritoneum which secure things inside the cavity to the abdominal wall -

Double sheets of peritoneal membrane. Suspend portions of digestive tract within peritoneal cavity. Connect parietal and visceral peritoneum. Provide a route to and from digestive tract for blood vessels, nerves, and lymphatic vessels. Stabilize positions of attached organs. Prevent intestines from becoming entangled.

Adipose tissue in Greater Omentum (Lesser omentum connects stomach to liver): -

Conforms to shapes of surrounding organs. Pads and protects surfaces of abdomen. Provides insulation to reduce heat loss. Stores lipid energy reserves.

Figure 24-2b The Mesenteries

B. Diagrammatic view of the organization of mesenteries in an adult. As the digestive tract enlarges, mesenteries associated with the proximal portion of the small intestine, the pancreas, and the ascending and descending portions of the colon fuse to the

January 9th, 2018

1080 Anatomy & Physiology

Figure 24-2d The Mesenteries

body wall D. Sagittal section showing the mesenteries of an adult. Notice that the pancreas, duodenum, and rectum are retroperitoneal.

Histology of Digestive Tract -

Major Layers of digestive (deep to superficial) tract include Mucosa (including mucosal epithelium, lamina propria, and muscularis mucosae), Submucosa, Muscular layer, and Serosa (visceral peritoneum).

Lining of Digestive Tract Varies by Region -

Longitudinal folds in empty stomach. Permanent transverse folds in small intestine. (circular)

Mucosa is the inner lining of the digestive tract. Myenteric Plexus controls the muscles within the muscular layer. Just under Submucosa is the Submucosal Neural plexus; controls muscle in submucosa and mucosal layers of digestive tract epithelium. Digestive epithelium - Mucosal epithelium is simple or stratified. Depending on location, function, and stresses. - Oral cavity, pharynx, esophagus, anal canal (high mechanical stress) – stratified squamous epithelium. - Stomach, small intestine, most of large intestine – simple columnar epithelium. Enteroendocrine cells – secrete hormones that coordinate activities of digestive tract and accessory glands. Lamina propria & Muscularis mucosae ** just need to know about the layers and basic function. Submucosa - Layer of dense irregular connective tissue – contains submucosal plexus - Binds mucosa to muscular layer - Numerous blood vessels and nerves Muscular Layer - Dominated by smooth muscle cells - Inner circular and outer longitudinal layers. - Involved in mechanical digestion and moving materials along digestive tract - Movements coordinated by enteric nervous system (ENS) - Oblique muscle in stomach (to allow twist/turn motion) Myenteric Plexus - Network of parasympathetic ganglia, sensory neurons, interneurons, etc.

1080 Anatomy & Physiology

January 9th, 2018

Serosa - Serous membrane covering muscular layer - Along most portions of digestive tract enclosed by peritoneal cavity - Adventitia (dense networks of collagen fibers) firmly attach digestive tract to adjacent structures No serosa on organs outside of cavities Motility of digestive tract - Visceral smooth muscle layer - Rhythmic cycles of activity - Controlled by pacesetter cells that undergo spontaneous depolarization - Wave of contraction spreads throughout Peristalsis (propulsion) - Waves of muscular contractions that move a bolus along length of GI tract - Circular muscled contract behind bolus and relax ahead of bolus - Longitudinal muscled ahead contract, and behind relax - Wave of contraction in circular muscle layer which forces bolus forward Segmentation (mechanical digestion) - Cycles of contraction that churn and fragment the bolus mixing contents with intestinal secretions Presence of food (pH) and volume (stretch) within digestive tract release hormones and secretions from cells that have short (myenteric plexus) and long (CNS) reflexes Oral cavity - Sensory analysis of food - Mechanical digestion through teeth tongue and palate surfaces - Lubrication by mucus and saliva - Limited chemical digestion of carbs (salivary amylase which begin to digest carbs) and lipids (lingual lipase to start digesting lipids) Oral mucosa - Lining of oral cavity - Stratified squamous epithelium - Relatively thin and nonkeratinized on cheek lips and inferior surface of tongue (aka sublingual medication is absorbed directly into blood stream due to this thin lining) - Thin, vascular mucosa inferior to tongue can rapidly absorb lipid-soluble medication - Oral vestibule space between cheeks and tongue Pharyngeal tonsils (adenoids) and palatine tonsils Tongue - Four primary functions

1080 Anatomy & Physiology -

January 9th, 2018

Mechanical digestions by compression, abrasion, and distortion Manipulation to assist in chewing and prepare food for swallowing Sensory analysis by touch, temp, and taste receptors Secretion of mucins and lingual lipase (starts digesting lipididdies)

Tongue muscles Teeth - incisors, canines (cuspids), premolars (bicuspids), molars - incisors are blade shaped, located at front of mouth, used for clipping or cutting, have a single root - canine teeth are conical, single pointed cusp, used for tearing or slashing, have single root. - Premolar – flattened, two prominent, rounded cusps, used to crush mash and grind, have one or two roots. Deciduous and permanent teeth (20 to 32) Salivary glands - Three major pairs secrete into oral cavity - Each has distinctive cellular organization and produces saliva with slightly different properties - Parotid, Sublingual, and submandibular Saliva -

Glands produce 1-1.5 liters a day 70 percent submandibular 25 percent from parotids 5 percent from sublingual

Functions of saliva - cleaning oral surfaces - moistening and lubricating food - keeping pH of mouth near 7 - controlling populations of bacteria and limiting acids they produce - dissolving chemicals that stimulate taste buds - initiating digestion of complex carbohydrates with salivary amylase Regulation of salivary secretions - salivary glands have para/sympathetic innervation - stimulated by any object in mouth, other brainstem nuclei, and activities of higher centers - parasympathetic stimulation accelerates secretion by all salivary glands Mastication (chewing) - food is forced from oral cavity to vestibule Pharynx Naso, oro, and laryngopharynx.

1080 Anatomy & Physiology

January 9th, 2018

Food travels through pharynx the same way air does. Esophagus - hollow muscular tube - conveys food and liquids to stomach - about 25cm long and 2cm wide - begins posterior to cricoid cartilage - enters abdominopelvic cavity Histology of esophagus - mucosa, submucosa, and muscular layer. - No serosa, adventitia is a collagen fiber framework instead. Deglutination (swallowing) - Can be initiated voluntarily, proceeds automatically Stomach - Temporary storage of ingested food - Mechanical digestion with muscular contraction - Chemical digestion of food with acid and enzymes - Chyme: partially digested food mixed with acidic secretions of stomach (kime) Parts of stomach - Fundus extends above esophagus - Cardia is just inferior to esophagus - Middle is the body - Bottom is the pyloric portion of the stomach (antrum, canal, pylorus, pyloric orifice) and the pyloric sphincter. Rugae -

Folds in stomach Flatten out as stomach expands Allow for expansion of gastric lumen up to 50x Muscularis mucosae and muscular layer Contains extra layers of smooth muscle such as oblique layer in addition to longitudinal and circular

Histology - Within mucosa of stomach are gastric pits which are pits ending in gastric glands which allow for different types of secretions to help break down food. - Gastric glands have G cells, parietal cells, and chief cells. And D cells - G cells secrete gastrin which stimulates secretion by parietal and chief cells and contractions of gastric wall - Parietal cells secrete; indirect hydrochloric acid (via hydrogen ions and chloride ion as well as intrinsic factor) - Chief cells secrete pepsinogen which is activated by HCl to become pepsin

1080 Anatomy & Physiology -

January 9th, 2018

D cells release somatostatin acts against gastrin. So there is a balance with the G cells.

Chemical digestion in stomach - Some digestion of carbs and lipids - As stomach contents become more fluid, pH approaches 2 and preliminary digestion of proteins by pepsin increases - Nutrients are not absorbed by stomach Phases - Cephalic phase: - Gastric phase: - Intestinal phase: Chemoreceptors tell the brain that something (food or drink) is diluting the acidity of the stomach atmosphere and therefore response takes effect Duodenal stretch and chemoreceptors look for presence of lipids and carbs which sends message to stomach to say ‘you’re done’ via Secretin which stop chief cells and parietal cells and peristalsis. Pancreas - Lies posterior to stomach - Extends from duodenum toward spleen - Retroperitoneal - Bound to posterior wall of abdominal cavity - Wrapped in thin, connective tissue capsule - Has endocrine and exocrine secretions - Secreted through duodenal papilla via pancreatic duct - Secretes alpha-amylase- a carbohydrase, breaks down certain starches, almost identical to salivary amylase - Pancreatic lipase – breaks down certain complex lipids, releases products aka fatty acids, that are easily absorbed. Nucleases break down RNA and DNA Proteolytic enzymes - Enzymes that break down proteins - Proteases break apart large protein complexes 4 common proteases: -

Trypsinogen gets converted to trypsin which is an enzyme cascade to activate other proteases Chymotrypsinogen converted to chymotrypsin Procarboxypeptidase converted to carboxypeptidase Proelastase converted to active elastase

1080 Anatomy & Physiology

January 9th, 2018

Histology of Liver - All lobes are mainly homogenous and have similar functionality - Porta hepatis: includes bile duct, hepatic portal vein, and hepatic artery proper - Hepatic portal system  UNDERSTAND Hepatic Portal System - All circulation from intestines and digestive tractive below esophagus travels back through hepatic portal vein. Hepatocytes - Liver cells - Function unit of liver is a LOBULE: 6 sided structure made of of hepatocytes and at each corner contains a portal triad (Interlobular bile duct, interlobular vein, and interlobular artery) - Sinusoids are capillaries and venules throughout the hepatic system for filtration and passing of nutrients, organic compounds, medications, etc. They are extensions of fenestrated capillaries. - Stellate macrophages within the sinusoids help attack bacteria, viruses, toxins, any pathogen of sorts, etc. - Bile canaliculi collect bile and pass it to the bile ducts perforating the lobules. Liver cells extract nutrients and rid the blood of toxins while passing through liver Physiology of liver - Liver has 200 functions - Metabolic action - Produces bile Production and function of bile - Bile salts in bile break lipid droplets apart (emulsification) in duodenum - Creates tiny emulsion droplets coated with bile salts - Increases surface area exposed to enzymes - Necessary because mechanical digestion in stomach creates large droplets of lipids - Pancreatic lipase can interact only at surface - Enterohepatic circulation Gallbladder - Hollow pear-shaped muscular sac - Stores and concentrates bile prior to secretion - Located in fossa in posterior surface of livers right lobe - Regions: fundus, body, and neck - Releases bile into duodenum when stimulated by cholecystokinin (CCK) - Without CCK, hepatopancreatic sphincter encircling lumen of bile duct remains closed - Bile exiting the liver in common hepatic duct enters cystic duct and is stored in gallbladder

1080 Anatomy & Physiology -

January 9th, 2018

When chime enters duodenum, CCK is released. Hepatopancreatic sphincter relaxes and gallbladder contracts. Liver secretes bile to gallbladder or duodenum

Small intestine - Long muscular tube where chemical digestion is completed and 90% of nutrient absorption occurs - Consists of duodenum, jejunum, ileum - Circular folds and villi to increase surface area for absorption - Villi are simple columnar epithelium - Lacteals help digest lipids via lymphatic circulation. Duodenum - Closest to stomach - Mixing bowl that receives chime - Submucosal glands release lots of mucus to remove acidity of the stomach - Mucus protects by releasing bicarbonate ions that raise pH Intestinal juices - Moisten chime - Assist buffering acids - Keeps digestive enzymes in working pH Central Reflexes - Gastroenteric reflex stimulates motility and secretion along entire small intestine - Gastroileal reflex triggers the opening of the iliocecal valve, allowing materials to pass from small to large intestines - Iliocecal valve controls passage of materials into large intestine Hormones of Duodenum - Gastrin: via G cells in response to proteins, increases stomach motility, production of acids and enzymes - Secretin released when chime enters duodenum, slows gastric muscle - Gastric Inhibitory peptide (GIP): inhibits gastric motility and secretion when fat is present in small intestine - Cholecystokinin releases bile from liver and gallbladder - Vasoactive intestinal peptide: increases activity and dilating capillaries and inhibits acid production in stomach - Enterocrinin: released when chime enters duodenum; stimulates alkaline mucus production by submucosal glands - Graphic on page 920 figure 24-23

Large intestine - Horshoe shaped

1080 Anatomy & Physiology -

January 9th, 2018

Extends from end of ileum to anus Lies inferior to stomach and liver Frames the small intestine About 1.5 meters long and 7.5 meters wide

Function is to store waste and absorb water back into system Components - Cecum - Colon (ascending, transverse, descending, sigmoid, rectum) - Anus Teniae coli run the length of the large intestine – they are longitudinal muscles that allow for stretching and compression of large intestine. They create the pouch-like appearances of Haustra. Rectum forms last 15cm of digestive tract Internal and external anal sphincter Internal under CNS control External under PNS Histology of large intestine - No villi - Abundance of goblet cells - Distinctive intestinal glands – deeper than glands of small intestine and dominated by goblet cells - Mucus provides lubrication for fecal material - Large lymphoid nodules scattered throughout lamina propria and submucosa Function: - Absorb water, nutrients, bile salts, organic wastes, vitamins and toxins produced by bacteria - Compaction of intestinal contents into feces Microbiome - Microbes (bacteria, fungi, and viruses) that live in and on human body including those that inhabit large intestines Vitamins - organic molecules, important as cofactors or coenzymes in metabolism; normal bacteria in colon make three vitamins that supplement diet. Vitamin K required by liver for four clotting factors including prothrombin Biotin is important in glucose metabolism Vitamin B5 is required in manufacturing of steroid hormones and some neurotransmitters

1080 Anatomy & Physiology

January 9th, 2018

Organic wastes – bacteria break down peptides in feces and generate: ammonia as soluble ammonium ions, indole and skatole (nitrogen containing compounds) Motility or large intestine - gastroileal and gastroenteric reflexes move materials into cecum while you eat - movement from cecum to transverse colon is very slow, allowing hours for water absorption - peristaltic waves move material along colon and segmentations movements mix contents of adjacent haustra. Defecation reflex is brought on by the distension of the rectum – sends feedback to short reflex which controls muscles in sigmoid colon to push more fecal material into rectum. Page 927 about secretion and breakdown Figure 24-27 chemical events of digestion Lipids absorbed into lymphatic system through lacteals Ion absorption Vitamins – fat-soluble and water-soluble Fat soluble vitamins means if the body has a source, then any extra is stored in your fat cells....