Introduction
Cardiovascular system: a pump (the heart) that delivers blood to vessels (arteries) that circulate blood throughout the body; materials in blood are exchanged with cells through tiny vessels (capillaries); blood is returned to the heart by another group of vessels (veins)
- pulmonary circuit: blood vessels that carry blood to & from the lungs
o sends deoxygenated blood to lungs to pick up oxygen & unload carbon dioxide
- systemic circuit: blood vessels that carry oxygenated blood to body tissues & return deoxygenated blood with wastes to heart
Structure of Heart
- heart size varies; an average adult heart is about 14 cm long x 9 cm wide
- heart is within mediastinum; bordered laterally by lungs, posteriorly by vertebral column & anteriorly by sternum
- extends 12-14 cm within mediastinum, from 2nd rib to 5th intercostal space
- base: attaches to large vessels; superior/posterior aspect of heart
- apex: pointed inferiolateral aspect of heart; pointed slightly to left
- pericardium: double-walled sac enclosing heart
- fibrous pericardium: outer dense connective tissue layer
o anchors heart to surrounding structures (diaphragm, vessels)
- serous pericardium: deep to fibrous pericardium
o parietal layer: lines internal surface of fibrous pericardium
o visceral layer (epicardium) – deep to parietal layer; outer layer of heart wall
- skeleton of the heart: fibrous connective tissue anchored to vessels & septum; strengthens & holds tissue together
Layers of heart wall:
- epicardium: visceral layer of serous pericardium; often accumulates fat
- myocardium: cardiac muscle deep to epicardium; bulk of heart tissue
o branched cardiac muscle cells linked by connective tissue fiber bundles (collagen & elastin) – fibrous skeleton of heart
- endocardium: thin inner myocardial surface; sheet of endothelium (squamous epithelium) resting on connective tissue
- lines chambers & valves; continuous with endothelial linings of major vessels
Heart Chambers & Valves
- atria: upper chambers; receiving chambers for blood
o auricles: small protruding appendages that slightly increase atrial volume
o right atrium receives deoxygenated blood from superior vena cava (from areas above diaphragm), inferior vena cava (from areas below diaphragm), & coronary sinus (from myocardium)
o left atrium receives oxygenated blood from pulmonary veins (4, from lungs)
- ventricles: lower chambers; discharging (pumping) chambers for blood
o papillary muscles: conelike muscle bundles in ventricular cavity; attached to tendon (chordae tendineae) that play a role in valve function
o right ventricle pumps blood into pulmonary trunk (to lungs)
o left ventricle pumps blood into aorta (to systemic circulation/body tissues)
- septum: separates atria & ventricle on left side from right side
- atrioventricular (AV) valves: prevent backflow of blood from ventricles to atria
o tricuspid valve: right AV valve; has 3 cusps (flaps of endocardium reinforced with CT)
o bicuspid (mitral) valve: left AV valve
o chordae tendineae: collagen cords attached to AV valve flaps; anchor cusps to papillary muscles
- semilunar (SL) valves: prevent backflow of blood from great vessels to ventricles
o aortic valve: prevents blood from flowing back into left ventricle following ventricular contraction
o pulmonary valve: prevents blood from flowing back into right ventricle following ventricular contraction
Pathway of blood through heart:
- pulmonary circuit: blood vessels that carry blood to & from the lungs
- systemic circuit: blood vessels that carry oxygenated blood to & from body tissues
- superior & inferior vena cava and coronary sinus ® right atrium ® (tricuspid valve) ® right ventricle ® (pulmonary semilunar valve) ® pulmonary trunk ® pulmonary arteries ® lungs ® pulmonary veins ® left atrium ® (bicuspid valve) ® left ventricle ® (aortic semilunar valve) ® aorta ® body tissues
Coronary Circulation: functional blood supply of heart (myocardium)
- coronary arteries: arise from the base of the aorta; carry oxygenated blood to myocardium of atria & ventricles
- cardiac veins: carry deoxygenated blood from myocardium to coronary sinus, which empties into right atrium
- proper circulation (constant blood supply) to myocardium is critical; blockage of coronary arterial circulation can be serious/fatal
o collateral circulation: smaller branches of coronary arteries have connections (anastomoses) for alternate blood pathways
o angina pectoris: chest pain due to short block of blood supply to myocardium
o myocardial infarct (MI, heart attack or coronary): can result from prolonged blockage
Heart Actions & Cardiac Cycle
- Cardiac cycle: all events associated with blood flow through heart
o systole: contraction
o diastole: relaxation (dilation or expansion)
o sequence:
§ ventricular filling (mid to late ventricular diastole)/atrial systole
§ ventricular systole/atrial diastole
§ early ventricular diastole
§ relaxation
- Heart sounds: lub-dup sound
o AV valves close (lub); SL valves close (dup)
o murmurs: sounds often indicative of valve problems
Cardiac Conduction System
- sequence of excitation:
o sinoatrial (SA) node: autorhythmic cells here are the fastest to generate impulses (~75/min, called sinus rhythm); hence, this is the heart¹s pacemaker
o atrioventricular (AV) node: receives impulses from SA node; fewer connections between cells delay impulse long enough for atria to complete contraction; also autorhythmic cells here, but slower impulses (~50-60/min, called junctional rhythm), so these cells do not set the pace unless there is damage to SA node cells
o atrioventricular (AV) bundle (bundle of His): electrical connection between atria & ventricles; transmits impulse to ventricles
o right & left bundle branches: sends impulse along cells of interventricular septum toward apex
o Purkinje fibers: extend from inferior aspect of interventricular septum to apex & into outer walls of ventricles
- Electrocardiography
o Electrocardiograph: measures electrical currents generated during heart contraction with a series of electrodes placed on 12 body regions
o Electrocardiogram (ECG or EKG): recording from electrocardiograph
§ P wave: atrial depolarization
§ QRS complex: ventricular depolarization
§ T wave: ventricular repolarization
§ P-Q interval: beginning of atrial depolarization until beginning of ventricular depolarization
§ Q-T interval: beginning of ventricular depolarization until beginning of ventricular repolarization
- Regulation of heart rate:
o Sympathetic division of ANS: increases heart rate
§ stimulated by cardioacceleratory center in medulla oblongata
o Parasympathetic division of ANS (vagus nerve): decreases heart rate
§ stimulated by cardioinhibitory center in medulla oblongata
o hormones:
§ epinephrine & norepinephrine: increases heart rate
§ thyroxine: slow sustained increase in heart rate
o ions: calcium, sodium & potassium
Blood Vessels
Structure of Blood Vessel Walls:
- tunica interna (tunica intima): innermost tunic (layer)
o endothelium (simple squamous epithelium) lining lumen of all vessels
- tunica media: middle tunic
o mostly smooth muscle cells & sheets of elastin fibers
o generally thickest layer in arteries
o smooth muscle innervated by vasomotor fibers of sympathetic division of ANS
§ vasoconstriction: reduced lumen diameter due to smooth muscle contraction
§ vasodilation: increase in lumen diameter due to smooth muscle relaxation
- tunica externa (tunica adventitia): outermost tunic
o mostly loose collagen fibers; protect & reinforce vessel wall & anchor it to surrounding structures
o contains nerve fibers, lymphatic vessels, & elastin in larger veins
Arteries: transport blood away from the heart
- elastic (conducting) arteries: thick-walled arteries near heart (aorta & branches)
- muscular (distributing) arteries: branch from elastic arteries to distribute blood to body organs; includes most named arteries
- arterioles: vary in size; lead from muscular arteries to capillary beds
o blood flow into capillary beds determined by arteriole diameter
o if arterioles constrict, tissue is largely bypassed
Capillaries: smallest blood vessels; exchange materials (gases, nutrients, hormones, etc.) in blood with tissues
- only tunica interna (endothelium)
- microcirculation: flow of blood from arteriole to venule
- precapillary sphincter: at root of metarteriole & capillary; acts as valve to regulate blood flow into capillary (constricts to send blood through bed (using vascular shunt))
- capillary exchange of respiratory gases & nutrients: oxygen, carbon dioxide, most nutrients & cellular wastes pass between blood & interstitial fluid by diffusion
- fluid movement: pressure & capillary pores allow fluid to leave capillaries at arterial end of capillary bed, but most returns at venous end
o hydrostatic pressure: force exerted by fluid pressing against a wall
§ in capillaries, same as capillary blood pressure
§ capillary hydrostatic pressure tends to force fluids through capillary walls
§ interstitial fluid hydrostatic pressure pushes fluid back in
- colloid osmotic pressure: large non-diffusible molecules (proteins) draw fluid toward them through osmosis
o capillary colloid osmotic pressure: large molecules cannot move through capillary membrane; draw fluid in
Veins: transport blood toward heart
- venules: smallest veins; range from postcapillary venules (only tunica interna) to larger venules with additional one or two layers of smooth muscle cells & thin tunica externa
- veins: large vessels with all 3 tunics; vessel walls smaller & larger lumens than corresponding arteries
o capacitance vessels (blood reservoirs): at any given time, most blood in the body is within veins
o venous valves: formed from folds of tunica externa; flaps that prevent backflow of blood, especially in limbs
Systemic Blood Pressure: blood pressure = cardiac output x peripheral resistance
- measured from brachial artery with sphygmomanometer
o uses auscultatory method (listening for filling of artery as pressure in cuff drops below arterial pressure)
o normal resting ranges: systolic BP: 110-140 mm Hg; diastolic BP: 75-80 mm Hg
o hypotension: low blood pressure (systolic BP below 100 mm Hg)
o hypertension: high blood pressure (sustained arterial pressure > 140/90)
- systolic pressure: pressure generated in aorta following (left) ventricular systole (~120 mm Hg)
- diastolic pressure: pressure in aorta following ventricular diastole (70-80 mm Hg)
- pulse pressure: systolic pressure – diastolic pressure
- cardiac output (CO): CO = Stroke Volume (SV) x Heart Rate (HR)
o normal resting values: SV = 70 ml/beat; HR = 75 beats/min; CO = 5250 ml/min
- resistance: opposition to blood flow (friction)
o peripheral resistance (PR): resistance in systemic circulation; contributed by blood vessel diameter, blood viscosity & blood vessel length
o blood viscosity: thickness of blood; more viscosity = greater resistance
o blood vessel length: longer vessel length = greater resistance
§ blood vessel diameter: most likely to alter resistance; decreased diameter = greater resistance
§ smooth muscle fibers control blood vessel diameter
Maintaining Blood Pressure:
- Short Term Regulation
o neural controls:
§ vasomotor center: sympathetic neurons in medulla oblongata integrate blood pressure control by altering cardiac output & blood vessel diameter
§ baroreceptor-initiated reflexes: baroreceptors = pressure-sensitive mechanoreceptors that respond to changes in arterial pressure & stretch
§ chemoreceptor-initiated reflexes: chemoreceptors respond to changing blood levels of oxygen, carbon dioxide & acidity
§ higher brain centers: hypothalamus (e.g.: fight or flight response) via medulla
o chemical controls:
§ adrenal medulla hormones; atrial natriuretic peptide (ANP); antidiuretic hormone; angiotensin II; nitric oxide (NO); inflammatory chemicals; alcohol
- Long Term Regulation: Renal regulation
o direct renal mechanism: blood volume altered through filtration in kidneys
o indirect renal mechanism: renin-angiotensin mechanism leads to aldosterone production
Systemic Circulation:
- major systemic arteries:
o aorta, aortic arch, descending aorta (thoracic & abdominal aorta)
o 3 branches from aortic arch: brachiocephalic artery, left common carotid artery & left subclavian artery
o common carotid arteries: serve head
§ vertebral & internal carotid arteries give off branches to form Circle of Willis in brain (several paths for blood to brain tissue)
o subclavian arteries: serve arms
o common iliac arteries: branch to internal iliac arteries (serve pelvic organs) & external iliac arteries (serve legs)
- major systemic veins:
o external & internal jugular veins: drain blood from brain, head & neck
o subclavian arteries: drain blood from arms
o brachiocephalic arteries: receive blood from jugular & subclavian veins & enter superior vena cava
o hepatic portal vein: receives blood from abdominal (digestive) organs & enters liver (metabolism & detoxification)
o common iliac veins: receive blood from internal iliac veins (from pelvic organs) & external iliac veins (from legs)
§ common iliac veins merge to form inferior vena cava
Chapter 14: Lymphatic System & Immunity
Introduction/Functions of the Lymphatic System
- draining excess interstitial fluid: lymphatic vessels drain excess fluid from tissue spaces & return it to the blood
- transporting dietary lipids: lymphatic vessels transport lipids & lipid-soluble vitamins (A,D,E & K) absorbed by GI tract to the blood
- carrying out immune responses: lymphatic tissue initiates specific immune responses to microbes or abnormal cells
Lymphatic Pathways: lymphatic capillaries ® lymphatic vessels ® subclavian veins
- lymphatic capillaries: microscopic closed-ended tubes that extend into interstitial spaces & receive lymph through their walls
- lymphatic vessels: walls similar to veins (thinner) with valves to prevent backflow
- large lymphatic vessels pass through lymph nodes & merge into lymphatic trunks
- lymphatic trunks lead to 2 collecting ducts: thoracic duct & right lymphatic duct
- collecting ducts join subclavian veins
Tissue Fluid & Lymph
- tissue fluid is formed from blood plasma; includes smaller proteins (excludes large)
- increased protein concentration in tissue fluid increases colloid osmotic pressure
- pressure increase forces some tissue fluid into lymphatic capillaries ® lymph
- lymph returns proteins with fluid to bloodstream & transports foreign particles to lymph nodes
- movement of lymph is generally slow due to low pressure; contraction of skeletal muscles & pressure due to breathing accelerates lymph movement
Lymphoid Organs: Thymus & Spleen
Thymus: located in mediastinum above heart
- composed of lymphatic tissue subdivided into lobules
- size is large at birth; shrinks during aging following puberty
- T lymphocytes mature (become fully active) in the thymus; the mature T cells then may migrate to other lymphoid tissues to provide immunity
Spleen: located in upper left quadrant of abdominopelvic cavity; under diaphragm & posterolateral to stomach
- resembles large lymph node subdivided into lobules
- islands of white pulp contains lymphocytes; surrounding red pulp contains red blood cells & some leukocytes
- sinuses within splenic lobules filled with blood; spleen is primary site for red blood cell breakdown
- macrophages in spleen filter foreign particles & begin breakdown of damaged RBCs
Body Defenses Against Infection: innate (nonspecific) & adaptive (specific)
- pathogens (bacteria, viruses, fungi, parasites, etc.) cause infection
Innate (Nonspecific) Defenses: includes species resistance, mechanical & chemical barriers, fever, inflammation & phagocytosis
- species resistance: each species is resistant to diseases that affect other species
- mechanical barriers: skin & mucous membranes; block entry of pathogens
- chemical barriers: enzymes & acid (low pH) in gastric juice kill pathogens; antimicrobials (lysozyme) in tears kills some pathogens
o interferons: proteins released by virus-infected cells that stimulate uninfected cells to synthesize antiviral proteins
§ stimulates phagocytosis, blocks viral replication, enhances WBC activity & slows tumor growth
- fever: increase in body temperature due to infection
o decreases blood iron level (slows bacterial growth) & increases phagocyte activity
- inflammation: tissue response to injury or infection
o 4 signs: localized redness, swelling, heat & pain
o chemicals released by damaged tissues attract WBCs to site
o inflammatory mediators: histamine from mast cells & basophils & other chemicals that cause vasodilation & increased blood vessel permeability
o fibrous CT may form a sac around injured tissue & block pathogen spread
- phagocytosis: neutrophils & macrophages destroy bacteria & foreign particles
o neutrophils enter infected tissue from blood; monocytes exit bloodstream & transform into macrophages that stay in tissues
o phagocytes associated with lining of blood vessels, bone marrow, liver, spleen, lungs & lymph nodes
Adaptive (Specific) Defenses: immune responses to specific pathogens & unwanted cells by antibodies from B lymphocytes & T lymphocytes
- antigens: molecules (especially proteins) that provoke an immune response
o during development, body learns to distinguish self antigens from nonself
o nonself antigens combine with surface receptors on B cells & T cells and stimulate an immune reaction
o haptens: small molecules that need carrier (larger molecule) to become antigenic
- lymphocytes are produced in red bone marrow & released into blood
o T cells mature in the thymus
o B cells mature in the bone marrow
o lymphatic tissues contain both T cells & B cells
- T cells interact with antigens directly ® cellular immune response
o T cells secrete cytokines (interleukins) that enhance cellular responses to antigens
o T cells may also secrete toxic substances that destroy target cells
- B cells interact with antigens indirectly ® humoral immune response
- T cells & B cells can form millions of different varieties to react against a wide variety of possible antigens
o each individual variety can interact with only one specific antigen
o members of each variety form a clone
- T cells & cellular immune response
o T cells activate when an antigen-presenting cell (APC) displays a foreign antigen
o macrophages phagocytize pathogen or large antigen, partially digests proteins & displays antigens on cell surface in association with major histocompatibility complex (MHC or HLA) protein
o helper T cell: activated by binding antigen/HLA complex on APC
§ when helper T cell binds antigen/HLA complex on B cell, it releases cytokines that stimulate B cell & T cell proliferation & attracts macrophages for phagocytosis
o cytotoxic T cells recognize antigen/HLA complexes on tumor cells or virus-infected cells & destroy these cells with perforin proteins
o memory T cells respond quickly to subsequent antigen exposure
- B cells & humoral immune response
o a B cell becomes activated when antigen binds to cell surface receptors; activation may be enhanced by helper T cell stimulation
o an activated B cell generates a clone that produces memory B cells & plasma cells that secrete antibodies
o antibodies bind to & generally inactivate the antigen
o B cells & their antibodies can defend against millions of different antigens by forming different antigen-binding sites on antibodies
- 5 classes of antibodies (immunoglobulins)
o antibodies are soluble proteins consisting of 4 polypeptide chains (2 heavy chains, 2 light chains) that form a Y-shaped structure
o each antibody has 2 antigen-binding sites at variable regions of chains
o IgD: B cell antigen receptor
o IgM: pentamer in blood; first Ig class secreted; agglutinating agent; activates complement
o IgG: most abundant antibody in blood; protects against bacteria, viruses & toxins; activates complement; crosses placenta
o IgA: dimer found in secretions (mucus, saliva, sweat intestinal juice, milk), helps to prevent pathogens from entering body
o IgE: normally rare in blood (increase during allergic reaction), binds to mast cells & basophils & causes release of histamine & other mediators of inflammation
- antibody actions
o antibodies bind to antigens, activate complement, & stimulate tissue inflammation
o antigen binding results in agglutination, precipitation or neutralization
o activated complement attracts phagocytes, makes foreign cells more susceptible to phagocytosis & ruptures foreign cell membranes (lysis)
- primary & secondary immune responses
o primary immune response is body¹s first response to antigen; antibodies are produced for several weeks & long-lived memory cells are produced
o secondary immune response uses memory cells to react quickly to subsequent exposure to previously encountered antigen
- practical classification of immunity
o active immunity: produce own antibodies; passive immunity: given antibodies
o naturally acquired active immunity: produced through antigens from infections
o artificially acquired active immunity: produced through antigens from vaccines
o naturally acquired passive immunity: antibodies pass from mother to child
o artificially acquired passive immunity: antibodies acquired from immune serum
- allergic reactions
o allergic reactions are excessive immune responses to antigens (allergens) that may damage tissue
o repeated exposure to antigens can result in delayed hypersensitivity that can cause skin inflammation
o immediate hypersensitivity results from overproduction of IgE against allergen
o allergy results from mast cells releasing histamine, prostaglandin & leukotrienes that cause tissue inflammation, contraction of bronchial & intestinal smooth muscles & increased mucus production
o allergy symptoms include hives, hay fever, asthma, eczema & gastric disturbance
- transplantation & tissue rejection
o tissue rejection occurs when immune system of transplant recipient reacts against donated tissue
o matching donor & recipient tissue antigens (MHC antigens (HLA in humans) on cell surface of tissue cells) & immunosuppression can minimize tissue rejection
o immunosuppressive drugs may, however, increase likelihood of infection
- autoimmunity
o in autoimmune disorders, the immune system produces autoantibodies that attack a person¹s own body tissues
o autoimmunity may result from a previous viral infection, faulty T cell development or a nonself antigen that resembles self antigen
Chapter 15: Digestion & Nutrition
Introduction
- digestion: mechanical & chemical breakdown of food & absorption of nutrients
- alimentary canal: continuous passageway (8m long) created by organs of digestion
o mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus
- accessory organs: organs that are not part of the GI tract, but participate in digestion
o salivary glands, liver, gallbladder, pancreas
General Characteristics of Alimentary Canal
- wall of GI tract consists of 4 layers
o mucosa: innermost layer, lines lumen; stratified squamous or simple columnar epithelium with mucus-secreting glands; folded in stomach & intestine to increase surface area for absorption; lined with thin layers of connective tissue & smooth muscle
o submucosa: loose CT, glands, blood vessels, lymphatics & nerves (plexuses)
o muscularis externa: 2 layers of smooth muscle (inner circular & outer longitudinal layers) that produce movements of tube to propel food
o serosa: visceral peritoneum; fibrous CT; secretes serous fluid to reduce friction
- mixing movements by rhythmic contractions of smooth muscle to crush food & mix with enzymes
- propelling movements: wavelike contraction (peristalsis) of alternate smooth muscle layers to propel food along tube
Mouth: receives food & begins mechanical & chemical digestion; includes oral cavity & vestibule (between teeth & cheeks/lips)
- cheeks: outer layers of skin, pads of fat, muscles associated with expression & chewing & inner lining epithelium
- lips: highly mobile with skeletal muscle, sensory receptors & rich blood supply
- tongue: rough surface for gripping food & mixing with saliva
o surface contains papillae with taste buds
o lingual tonsils (immune cells) at root of tongue
- palate: roof of oral cavity has hard palate formed from bone & mucosal soft palate
o uvula at tip of soft palate closes off nasal cavity during swallowing
o palatine tonsils: at either side of opening to throat at back of oral cavity
- teeth: begin mechanical digestion by breaking food into smaller pieces to increase surface area for chemical digestion
o 20 primary & 32 secondary teeth
o each tooth consists of crown (above gums) & root (below gums) & composed of enamel (calcium phosphate coating over crown), dentin (bulk of tooth), pulp, nerves & blood vessels
o periodontal ligament attaches tooth to alveolar process in maxilla or mandible
Salivary Glands: secrete saliva, which moistens food & begins chemical digestion of carbohydrates, dissolves food chemicals for taste & cleanses mouth
- salivary glands include serous glands that secrete digestive enzymes & mucous glands that secrete mucus
- parotid glands (anterior/inferior to ear) secrete amylase, an enzyme that digests carbohydrates
- submandibular gland secrete viscous saliva (serous fluid & mucus)
- sublingual gland secretes mucus
Pharynx & Esophagus: food passageways to stomach
- pharynx is divided into nasopharynx, oropharynx & laryngopharynx
- swallowing stages: food mixed with saliva & forced into pharynx; involuntary reflexes move food into esophagus; peristalsis transports food to stomach
- esophagus: passes through diaphragm & joins stomach at cardiac sphincter
- cardiac sphincter: smooth muscle valve that prevents backflow of food from stomach
Stomach: receives food, mixes it with acidic gastric juice, begins chemical digestion of proteins, absorbs limited materials, & moves food into small intestine
- stomach divided into cardiac, fundic, body & pyloric regions
- pyloric sphincter: valve to prevent backflow between stomach & small intestine
- gastric glands secrete gastric juice containing pepsin (protease; digests proteins), hydrochloric acid (HCl) and intrinsic factor (required for vitamin B12 absorption)
- parasympathetic impulses & the hormone gastrin enhance gastric secretion
- reflexes due to food in small intestine inhibit gastric secretion
- a few substances (water, small molecules) may be absorbed from the stomach wall
- mixing movements help produce chyme; peristalsis moves chyme into pyloric region & then small intestine
- rate of emptying depends on fluidity of chyme & type of food present
Pancreas: produces pancreatic juice containing digestive enzymes that is moved into the duodenum of the small intestine through the pancreatic duct
- pancreatic juice contains enzymes that digest carbohydrates (amylase), proteins, fats & nucleic acids
- pancreatic juice has a high bicarbonate ion concentration (alkaline) that helps neutralize chyme
- the hormone secretin stimulates release of pancreatic juice with bicarbonate ions
- the hormone cholecystokinin (CCK) stimulate release of pancreatic juice with enzymes
Liver: metabolizes carbohydrates, lipids and proteins; stores some substances; filters blood; destroys toxins & secretes bile
- left & right lobes contain hepatic lobules that secrete bile; bile is carried to hepatic ducts & flows into either cystic duct into gallbladder (storage) or common bile duct into duodenum of small intestine
- in small intestine, bile salts act as an emulsifier (mix lipids & water) to help digestion & absorption of lipids (fatty acids & cholesterol) & fat-soluble vitamins
- bile contains bile salts made from cholesterol, bile pigments (bilirubin), & electrolytes
- gallbladder stores bile between meals; gallbladder located under right lobe of liver
- the hormone cholecystokinin (CCK) stimulate release of bile
- sphincter muscle at base of common bile duct controls bile flow into duodenum
Small Intestine: receives pancreatic juice from pancreas & bile from liver &/or gallbladder, completes digestion of food, absorbs nutrients, and transports residues to large intestine
- small intestine consists of duodenum, jejunum & ileum
- wall is lined with villi (folds) that increase surface area & aid in mixing & absorption
- intestinal glands located between villi
- secretes mucus & digestive enzymes (break down sugars, proteins & fats)
- gastric juice, chyme & stretch reflexes stimulate secretions
- enzymes on microvilli of mucosal cells complete digestion
- villi absorb monosaccharides, amino acids, fatty acids & glycerol; nutrients move through mucosal cells & into capillaries
- long-chain fatty acids absorbed by lacteals (lymphatic capillaries); short-chain fatty acids absorbed by blood capillaries
- mixing movements & peristalsis propel material through small intestine
- ileocecal sphincter controls movement of materials into large intestine
Large Intestine: reabsorbs water & electrolytes; forms, stores & eliminates fecal waste
- large intestine consists of cecum, colon, rectum & anal canal
- colon divided into ascending, transverse, descending & transverse colon
- tissue of wall similar to stomach & small intestine, but longitudinal muscle layer arranged in distinct bands (teniae coli); muscle tension forms pouches (haustra)
- forms mucus; little to no digestive function
- movements similar to small intestine; mass movements 2-3 times daily
- defecation reflex stimulates defecation to remove waste
- internal anal sphincter (smooth muscle) & external anal sphincter (skeletal muscle) control removal of waste
- feces consist of water, undigested material, electrolytes, mucus & bacteria
- color of feces due to bilirubin pigment of bile converted to dark pigment by bacteria
Nutrition: study of nutrients & how the body utilizes them
- macronutrients (carbohydrates, lipids & proteins) required in large amounts; micronutrients (vitamins & minerals) required in smaller amounts
- calories measure potential energy in foods
o calorie is amount of energy needed to raise temperature of 1g of water by 1šC
o kilocalories (Cal) are used to measure potential energy in macronutrients
o carbohydrates & proteins yield ~ 4 Cal/gram; lipids yield ~ 9 Cal/gram
- carbohydrates: used primarily to supply energy for cellular processes
o carbohydrates include sugars (monosaccharides & disaccharides) & complex carbohydrates (starch, glycogen & cellulose)
o starch from grains & vegetables; glycogen from meats; disaccharides from cane sugar; monosaccharides from honey & fruit
o cellulose (in plant cell walls) cannot be digested by humans ® fiber; provides bulk that assists movement through GI tract
o energy is released from glucose through oxidation (aerobic cellular respiration)
o lipids & proteins can be utilized for energy in most cells if glucose levels low
o neurons require constant supply of glucose
o excess glucose is stored as glycogen or converted to fat (stored in adipose tissue)
o carbohydrates required to synthesize nucleic acids & breast milk
o carbohydrate requirements vary for different people depending on activity
- lipids: supply energy for cellular processes & aid in building structures such as cell membrane & molecules such as steroids
o lipids include fats (mostly triglycerides), phospholipids & cholesterol
o saturated fats found in meats, eggs, milk & some oils; unsaturated fats found in seeds, nuts & plant oils (monounsaturated fats in olive, peanut & canola oils considered healthiest); cholesterol in egg yolk, milk, butter, cheese & meats
o digestion breaks down triglycerides to fatty acids & glycerol
o beta oxidation releases acetyl coA from fatty acids; acetyl coA can be used for energy or converted to ketone bodies (acetone)
o excess fatty acids & glycerol stored in adipose tissue
o linoleic acid, linolenic acid & arachidonic acid are essential fatty acids (required in diet)
o liver synthesizes triglycerides, phospholipids, lipoproteins (transport lipids in blood) & cholesterol
o cholesterol used in synthesis of bile salts, steroid hormones, membranes & vitamin D
o fat intake requirements also vary for individuals; must be sufficient to carry fat-soluble vitamins (A, D, E & K)
- proteins: wide variety of functions... enzymes control metabolism in cells; clotting factors clot blood; structural proteins include keratin of skin & collagen of connective tissue; plasma proteins regulate water balance; actin & myosin in muscle cells; hormones & antibodies in blood
o proteins can be broken down for energy; must be converted to amino acids & amino acids deaminated (removes amino group; converted to urea waste) & converted to acetyl coA
o proteins found in meats, fish, poultry, cheese, milk, nuts, eggs, cereals & legumes
o 8 amino acids (10 in children) are essential amino acids (required from diet)
o complete proteins provide all essential amino acids; meats provide complete proteins; vegetables must be combined for complete proteins (grain & legume)
o protein requirements: must have sufficient protein to supply all essential amino acids & to provide nitrogen for synthesis of nitrogen-containing compounds
- vitamins: organic molecules that are essential nutrients required for metabolism
o fat-soluble vitamins (vitamins A, D, E & K) are absorbed with lipids
o water-soluble vitamins (vitamin C & B vitamins) absorbed with water
o vitamin A can be synthesized from beta-carotene (antioxidant in orange vegetables) required for synthesis of visual pigments, normal development of bones, teeth & maintenance of epithelia
o vitamin D required for calcium & phosphorus absorption during digestion
o vitamin E is antioxidant (prevents oxidation of vitamin A & polyunsaturated fatty acids)
o vitamin K required for blood clotting
o B vitamins (B1-B12) required for cellular metabolism
o vitamin C (ascorbic acid) required for collagen production, storage of folic acid, & metabolism of some amino acids; promotes iron absorption & synthesis of steroid hormones
- adequate diets: provide sufficient energy & essential nutrients to support growth, maintenance & repair of tissues
o food guide pyramids can help to personalize diets
o malnutrition is poor nutrition due to lack of food or failure to utilize food
Chapter 16: Respiratory System
Introduction
- respiratory system includes tubes that remove particles from incoming air & transport air to & from lungs and air sacs where gases (oxygen & carbon dioxide) are exchanged
- respiration is entire process of gas exchange between atmosphere & body cells
o ventilation (breathing): moving air into & out of lungs
o external respiration: gas exchange between blood & air in lungs
o transport of gases in blood between lungs & body cells
o internal respiration: gas exchange between blood & tissue cells
Organs of Respiratory System
- nose: supported by bone (posteriorly) & cartilage (anteriorly)
o nostrils: openings for air
- nasal cavity: mucosa-lined passageway for air into nasopharynx; divided into left & right halves by nasal septum
o mucous membrane filters, warms & moistens incoming air
o nasal conchae divide nasal cavity into passageways & increase surface area to warm & moisten air
o ciliary action carries particles trapped in mucus to pharynx, where they are generally swallowed
- paranasal sinuses: spaces in bones of the skull lined by mucous membrane that open into nasal cavity
o located in maxillary, frontal, sphenoid & ethmoid bones
- pharynx: passageway for air & food behind nasal cavity (nasopharynx), oral cavity (oropharynx) & larynx (laryngopharynx)
- larynx (voice box): conducts air, helps prevent foreign objects from entering trachea & produces sounds of speech
o composed of muscles & cartilage; lined with mucous membrane
o contains vocal cords, which vibrate from side to side & produce sounds when air from lungs passes through them
o glottis: opening in larynx that serves as a passageway for air
o epiglottis: elastic cartilage at top of larynx that closes off larynx during swallowing
- trachea: extends into thoracic cavity to bronchi entering lungs; anterior to esophagus
o lined with C-rings of hyaline cartilage that helps keep airway open; cartilage incomplete at back, allows room for expansion of esophagus during swallowing
o divides into left & right bronchi that enter lungs
- bronchial tree: branched air passages that lead from trachea to air sacs in lungs called alveoli
o alveoli are at the distal end of alveolar ducts, the narrowest tubes of tree
- lungs: soft, spongy cone-shaped organs on either side of thoracic cavity
o mediastinum separates left & right lungs; diaphragm & thoracic cage enclose them
o left lung has 2 lobes & cardiac notch (space for heart); right lung has 3 lobes
o visceral pleura attaches to surface of lungs; parietal pleura lines thoracic cavity
o each lobe of lungs composed of alveoli, blood vessels & supporting tissues
Breathing Mechanism
- inspiration: atmospheric pressure forces air into lungs
o pressure in alveoli decreases due to contraction of breathing muscles (diaphragm & intercostals) & expansion of thoracic cavity
o when breathing muscles contract, thoracic cage moves upward & outward, increasing volume (decreases pressure)
o surface tension aids lung expansion
- expiration: increased pressure in lungs forces air out of lungs
o elastic recoil of lung tissues & surface tension within alveoli provide forces of expiration
o when breathing muscles relax. thoracic cage moves downward & inward, decreasing volume (increases pressure)
- respiratory air volume & capacities
o respiratory cycle: one inspiration followed by one expiration
o respiratory volumes measured with spirometer
o tidal volume (TV): air volume that moves into & out of the lungs with each breath (~ 500 ml)
o inspiratory reserve volume (IRV): air volume that can be forcibly inspired beyond tidal volume (~ 1900-3100 ml)
o expiratory reserve volume (ERV): air volume that can be forcibly expired beyond tidal volume (~ 700-1200 ml)
o residual volume (RV): air remaining in lungs after forced exhalation (~ 1200 ml)
o inspiratory capacity (IC): TV + IRV
o functional residual capacity (FRC): RV + ERV
o vital capacity (VC): TV + IRV + ERV
o total lung capacity (TLC): VC + RV
Control of Breathing
- normal breathing is rhythmic & involuntary
- respiratory center in brainstem includes portions of pons & medulla oblongata
o medulla rhythmicity center includes 2 groups of neurons
§ dorsal respiratory group controls basic rhythm of breathing
§ ventral respiratory group increases inspiratory & expiratory respiratory movements during forceful breathing
o pneumotaxic area regulates breathing rate (normally ~ 12 breaths/minute)
- factors affecting breathing: chemicals, stretching of lung tissues, emotional states
o central chemoreceptors associated with respiratory center
§ blood concentrations of carbon dioxide & hydrogen ions affect chemoreceptors; stimulation of receptors increases breathing rate
o peripheral chemoreceptors are in walls of certain large arteries
§ these chemoreceptors sense low oxygen levels; when oxygen levels are low, breathing rate increases
o overstretching lung tissue triggers inflation reflex
§ reflex shortens duration of respiratory movements & prevents overinflation of lungs during forceful breathing
o hyperventilation decreases blood carbon dioxide levels, but is very dangerous when done before swimming underwater
Alveolar Gas Exchange
- gas exchange between blood & air occurs at alveoli, tiny air sacs clustered at distal ends of alveolar ducts
- respiratory membrane: consists of alveolar & capillary walls
o site of gas exchange between blood & alveoli
- diffusion across respiratory membrane
o partial pressure of gas is proportional to concentration of that gas in a mixture or concentration dissolved in a liquid
o gases diffuse from regions of higher partial pressure to regions of lower partial pressure
o oxygen diffuses from alveolar air into blood
o carbon dioxide diffuses from blood into alveolar air
Gas Transport
- oxygen is primarily transported in red blood cells bound to hemoglobin protein (oxygen binds to iron of the heme group of hemoglobin)
o oxyhemoglobin is unstable & releases oxygen in regions where partial pressure of oxygen is low
o more oxygen is released as blood levels of carbon dioxide increase, as blood becomes more acidic, and as blood temperature increases
- carbon dioxide may be carried in blood, bound to hemoglobin, or as bicarbonate ion in blood
o most carbon dioxide is transported as bicarbonate ion
o enzyme carbonic anhydrase forms carbonic acid from carbon dioxide & water
o carbonic acid dissociates to release hydrogen ions & bicarbonate ions; buffering system in blood