Respiratory and Digestive Systems
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Cellular respiration, the cornerstone of all energy producing chemical reactions in the body uses ____________ and produces ___________ at the cellular level.
What two processes occur as part of the respiratory system that contribute to the critical function of using oxygen and producing carbon dioxide at the cellular level?
- pulmonary ventilation
- external respiration
What are the five important functions of the nose?
- -Provides an airway for respiration
- -Moistens and warms the entering air
- -Filters and cleans inspired air
- -Serves as a resonating chamber for speech
- -Houses olfactory (smell) receptors
What type of tissue comprises the respiratory mucosa that lines the nasal cavity?
Pseudostratified ciliated columnar epithelium
What is the purpose of the nasal conchae?
Increase mucosal surface area and enhance air turbulence so that debris can be trapped more efficiently.
What about the anatomy of the paranasal sinuses relative to the nasal cavity predisposes these structure to bacterial infections (sinusitis)?
Connected to the nasal cavity via narrow passageways which can become blocked by inflamed mucosa trapping bacteria in the sinus.
Which of the three divisions of the pharynx are lined by stratified squamous epithelium? Why?
- Oropharynx and Laryngopharnyx
- To protect it from food passage
What is the opening between the true vocal cords called?
Why do people who smoke cough so much ("smoker's cough")?
Smoking destroys cilia so coughing is only means of preventing mucous from accumulating in lungs.
Why are foreign bodies and aspiration pneumonias more common in the right lung?
Right main bronchus is wider, shorter and more vertical than the left.
What anatomic structures account for most of the lung's volume?
~300 million alveoli
What is the respiratory membrane? What is it composed of? How thick is it?
- where respiratory gas exchange occurs
- composed of the alveolar and capillary walls and their fused basement membranes
- ~0.5 microns thick
What are alveolar pores? What is their function?
- Connections between adjacent alveoli.
- Allow air pressure throughout lung to be equalized and provide alternate to alveoli whose bronchi have collapsed.
What is the function of type II alveolar cells?
Secrete surfactant and antimicrobial proteins
Which lung is smaller? Why?
The left lung, because it has the cardiac notch where the heart sits.
What is the adaptive reason that the lung is separated into lobes, segments and lobules by connective tissue septae?
Allows pulmonary disease to be confined to one or a few segments.
What two layers line the pleural space?
Parietal pleura and Visceral pleura
What are the two reasons that there is a small amount of fluid between the parietal and visceral pleura?
To provide lubrication and surface tension
What is pleural effusions? What are the three causes?
- Excess fluid in the pleural cavity
- -Left-sided congestive heart failure
Intrapleural pressure (Pip) is always __________ relative to intrapulmonary pressure (Ppul) due to the presence of ___________ within the pleural space.
- negative pressure
- small amount of pleural fluid
Any condition that equalizes intrapleural pressure with intrapulmonary or atmospheric pressure causes lungs to ___________.
What are the two types of homeostatic imbalances that result from the equalizing of the intrapleural and intrapulmonary pressures?
- Atelectasis - collapse of all or a portion of a lung
- Pneumothorax - injury to a parietal or visceral pleura causing air to enter pleural space
Quiet inspiration is a(n) ________ process and quiet expiration is a(n) ___________ process (in a healthy individual).
During inspiration the inspiratory muscles contract and intrapulmonary volume ________ which causes a(n) ___________ in intrapulmonary pressure.
Why does the process of intrapulmonary volume increase and intrapulmonary pressure decrease result in air flowing into the lungs?
Because of pressure gradient until Ppul = Patm
What are the three factors that can hinder air passage and pulmonary ventilation? Which of these factors increases in asthma?
- Airway resistance - increases in asthma
- Alveolar surface tension
- Lung compliance
In regard to autonomic nervous systems, _______ stimulation cause bronchoconstriction and _______ stimulation causes bronchodilation.
Medication that simulates the action of ________ nervous stimulation should be administered to those having an acute asthma attack.
What is the function of surfactant produced by type II alveolar cells?
- Reduces surface tension of alveolar fluid
- Discourages alveolar collapse
What are the three things that reduce lung compliance? Does this make pulmonary ventilation easier or harder?
- -Non-elastic scar tissue (fibrosis)
- -Reduced production of surfactant
- -Decreased flexibility of the thoracic cage (reduced thoracic walk compliance)
What is the volume of air that moves into and out of lungs with each breath of quiet respiration called? What is the "normal" volume?
Tidal volume (500mL)
What is the anatomical dead space? What is its "typical" volume?
Volume of the conducting zone conduits (~150mL)
What two categories of respiratory disease can pulmonary function tests help differentiate?
- Obstructive pulmonary disease
- Restrictive disorders
Which specific pulmonary function test is most useful in differentiating between obstructive pulmonary diseases and restrictive disorders? In which one will it be "below normal"?
- abnormal in obstructive lung disease
Which respiratory adjustment, taking deeper breaths or increasing respiratory rate is more effective at increasing alveolar ventilation rate (AVR)?
What is external respiration?
Oxygen enters and carbon dioxide leaves the blood in the lungs by diffusion.
What is internal respiration?
Oxygen enters and carbon dioxide leave the tissues.
Alveoli contain more ___________ and _____________ than the atmosphere. Why?
- carbon dioxide
- water vapor
- Due to gas exchanges in the lungs, humidification of the air, mixing of the alveolar gas that occurs with each breath.
Oxygen diffuses rapidly from the alveoli into the pulmonary capillary blood. Why?
Oxygen partial pressures reach equilibrium of 104 mm Hg in ~0.25 seconds, about 1/3 the time a red blood cell is in a pulmonary capillary.
Oxygen partial pressures reach equilibrium of 104 mm Hg in ~0.25 seconds, about 1/3 the time a red blood cell is in a pulmonary capillary. How does this improve our ability to deliver more oxygen to exercising muscles?
Because blood can flow through three times as quickly and still be adequately oxygenated.
Where alveolar oxygen partial pressures (Po2) are high, the arterioles ___________ and where Po2 is low, the arterioles ___________.
What two anatomic features allow for such high efficiency of the respiratory membrane? Which one is affected in pneumonia and congestive heart failure causing a reduction in gas exchange (external respiration)?
- Thickness - affected in pneumonia and CHF
- Surface area
In internal respiration partial pressures and diffusion gradients are ________ compared to external respiration. Why?
- Tissue cells continuously use oxygen and produce carbon dioxide.
98.5% of oxygen in the blood is transported by ____________.
hemoglobin (loosely bound to each Fe)
How many oxygen molecules does each hemoglobin contain when it is saturated?
As each successive oxygen binds at the respiratory membrane, hemoglobin shape changes and affinity for additional oxygen ___________. As each successive oxygen is released at the tissues, affinity of hemoglobin for oxygen ___________.
In arterial blood at rest (Po2 = 100 mm Hg), hemoglobin is ____% saturated.
Hemoglobin is almost completely saturated at a Po2 of 70 mm Hg. How does this help those at high altitudes and individuals with lung disease?
Because O2 loading and delivery to tissues is adequate when Po2 of inspired air is below normal levels.
Increases in concentrations of what four substances decrease the affinity of hemoglobin for oxygen (shift oxygen-hemoglobin dissociation curve to the right)?
- Amount of BPG in the blood (Biphosphoglycerate)
Why is the increase of temperature, H+, Pco2 and amount of BPG in the blood such an effective physiologic adaptation?
These factors see to it that Hb unloads much more O2 in the vicinity of hard-working tissue cells.
The majority of carbon dioxide in the blood is transported as _____________.
Bicarbonate ions (HCO3-) in plasma
The "Haldane effect" states that the lower the Po2 and hemoglobin saturation with oxygen, the _______________.
more CO2 can be carried in the blood
What ion is released when oxygen is taken up by hemoglobin at the lungs?
How does the release of H+ help unload carbon dioxide from the pulmonary blood?
because H+ combines with HCO3-
What chemical factor has the greatest influence on respiratory rate and depth? Through what type of receptors does this factor exert this influence?
- CO2 levels
- central chemoreceptors (medulla)
Under what circumstances does oxygen assume control of respiratory rate and depth?
When Po2 falls below 60 mm Hg
Why do drowning victims die by breathing water into their lungs?
Medulla centers override voluntary control when Pco2 levels become critical.
How does the respiratory system adjust to lower partial pressures of oxygen during the first few days spent at high altitudes (> 8000 feet)?
Chemoreceptors become more responsive to Pco2 when Po2 declines and a substantial decline in Po2 directly stimulates peripheral chemoreceptors.
Chronic obstructive lung disease (COPD) is characterized by an irreversible ______________.
decrease in the ability to force air out of the lungs
By far the greatest risk factor for COPD is ____________.
What two processes are responsible for the dyspnea (shortness of breath) experienced by those having an acute asthma attack?
- active inflammation of the airways
What are the six digestive processes that take place within the digestive system?
- mechanical digestion
- chemical digestion
What are the two layers of the peritoneum?
- visceral peritoneum - on external surface of most digestive organs
- parietal peritoneum - lines body wall
Where does an "intraperitoneal" organ lie and where does a "retroperitoneal" organ lie?
- intraperitoneal - between the two peritoneums
- retroperitoneal - lie posterior to the peritoneum
What is the function of the hepatic portal (venous) circulation?
Drains nutrient-rich blood from digestive organs and delivers it to the liver for metabolic processing before returning to the heart.
What are the functions of the mucosa lining the gastrointestinal (alimentary) tract?
- secretes mucus, digestive enzymes and hormones
- absorbs end products of digestion
- protects against infectious disease
What is the function of the muscularis externa? What are its two layers?
- responsible for segmentation and peristalsis
- inner circular and outer longitudinal layers
Although nervous control of the alimentary tract is largely _________, some extrinsic control is exerted by the autonomic nervous system with _________ impulses stimulating secretion and motility and ____________ inhibiting.
What structure is responsible for closing off the nasopharynx during swallowing?
What are the three extrinsic salivary glands?
What are the four functions of saliva?
- cleanses the mouth
- dissolves food chemicals so they can be tasted
- moistens food and aids in bolus formation
- contains enzymes that begin the breakdown of starch
What is the function of the intrinsic salivary glands?
To secrete continuously in amounts just sufficient to keep the mouth moist.
What type of tissue composes the mucosa of the esophagus? Why?
- Non-keratinized stratified squamous epithelium
What is the function of the esophagus?
food to pass from mouth to stomach
What structures form and reinforce the gastroesophageal sphincter?
Reinforced by surrounding diaphragm resulting in physiologic sphincter.
What is the function of the gastroesophageal sphincter?
Helps prevent "reflux" of stomach acid into esophagus
What homeostatic imbalance causes "heartburn"?
Gastroesophageal reflex disease (GERD)
What are the complications and risks of the chronic form of GERD?
Can lead to esophagitis/esophageal ulcers and can even increase the risk of esophageal cancer.
What enzyme starts the chemical digestion of carbohydrates (polysaccharides)? Where does this occur?
Why is there an extra layer of smooth muscle in the stomach compared with the rest of the alimentary (GI) tract?
Allows stomach to churn, mix, move and physically break down food.
What cells of the stomach mucosa secrete hydrochloric acid (HCl)?
Why does the stomach need such a highly acidic (pH 1.5 - 3.5) environment?
To denature protein in food, activates pepsin (protein digestion), and kills many bacteria.
What is the function of the intrinsic factor? What cells secrete it?
- Glycoprotein required for absorption of vitamin B12 in small intestine.
- Parietal cells
What do chief cells do?
Secrete inactive enzyme pepsinogen which is activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism)
What forms the mucosal barrier of the stomach? Why is this barrier necessary?
- Bicarbonate-rich mucus
- To withstand harsh acidic environment
What homeostatic imbalance results from a breakdown of the mucosal barrier of the stomach? What is the cause of this breakdown?
Peptic (gastric) ulcers - erosion of the stomach wall, 90% caused by H. pylori bacteria
What are the four functions of the stomach?
- Physical digestion
- Denaturation of proteins
- Enzymatic digestion of proteins
- Secretion of intrinsic factor
Which phase of gastric secretion lasts the longest and provides the most "gastric juice"? What hormone plays the greatest role in this phase? What cells secrete this hormone? On what cells does this hormone have its greatest effect?
- Gastric phase
- hormone gastrin
- gastrin-secreting enteroendocrine cells (G cells)
- greatest effect on HCl secreting parietal cells
What three chemicals are necessary for maximal HCl secretion by the parietal cells? How does the fact that all three are necessary effect treatment for hyperacidity?
- Acetylcholine, Histamine and Gastrin
- All three must bind to parietal cells otherwise HCl secretion is scant, antihistamines block histamine receptors in parietal cells and are used to treat hyperacidity
What are enterogastrones, what is their function and what stimulates their secretion?
- Intestinal hormones - secretin, cholecystokinin (CCK) and vasoactive intestinal peptide (VIP)
- Inhibit gastric secretion
- When chyme enters the duodenum
The majority of digestion and absorption occurs in the _______.
What three modifications for absorption of nutrients does the small intestine have? Which portion of the small bowel has the most of these? Why?
- -Circular folds (plicae circulares)
- Proximal portion of bowel
- Increase surface area by a factor of 600 for nutrient absorption
What is the purpose of the plicae circulares?
Forces chyme to slowly spiral through lumen (increasing time for absorption)
The villi and microvilli improve nutrient absorption by increasing _____________.
Where is the dense capillary bed, critical for obtaining and transporting nutrients, located in the small intestines?
In the Villi
Intestinal juice, secreted by the mucosa of the small intestine, is composed primarily of ____________, and is enzyme ______________.
Where do the majority of digestive enzymes that function in the small intestine come from?
The main function of the liver is to ______________________.
filter and process nutrient-rich blood
Liver lobules have a ____________ shape and serve as the liver's ____________.
- functional units
In cirrhosis, scarring of the liver can obstruct blood flow causing __________. The complication resulting from this condition that can cause patients to bleed to death is ___________.
- portal hypertension
- esophageal varices
What substance, secreted by the liver, aids in fat digestion in the small intestine? How does this substance perform this function?
- Large fat globules in duodenum are separated into millions of small, fatty droplets that provide large surface areas for fat-digesting enzymes to work on
What is the function of the gall bladder?
Stores bile not immediately necessary for digestion
What stimulates the secretion of bile by the liver?
Bile salts in enterohepatic circulation and secretin from intestinal cells exposed to HCL and fatty chyme
What stimulates gallbladder contraction and relaxation of the hepatopancreatic sphincter?
Cholecystokinin (CCK) from intestinal cells exposed to proteins and fat in chyme.
What induces the secretion of enzyme-rich pancreatic juice by the acini of the pancreas? What is it secreted by? What is it secreted in response to?
- Cholecystokinin (CCK)
- CCK is secreted by enteroendocrine cells of the mucosa of the small intestine
- Released in response to proteins and fat in small intestine
What is the predominant motion of the small intestine? Why is it preferred over peristalsis? When does peristalsis occur?
- Mixes and moves contents slowly and steadily toward ileocecal valve
- Peristalsis occurs in the late intestinal phase
What are the functions of the large intestine?
Absorb most of the remaining water in indigestible food residues
There are _________ of bacteria colonizing the colon. What function does this bacteria flora perform in the large intestine?
- 10 million different types
- Ferment indigestible carbohydrates (e.g. cellulose) and synthesize B complex vitamins and vitamin K
What is the gastrocolic reflex?
Activates slow moving, powerful peristaltic waves that move over large areas of the colon three or four times per day.
What is chemical digestion?
Catabolic process in which large food molecules are broken down to monomers (chemical building blocks) which are small enough to be absorbed by the GI tract lining.
Where are most nutrients transported after absorption from the small intestine?
to the liver via the hepatic portal vein
Where is carbohydrate digestions started, where is it finished? What type of enzymes do most of this work?
- Started in the mouth
- Finished in the small intestine
- Pancreatic amylase does most of the carbohydrate digestion
What enzyme starts protein digestion and where does this occur? What organ secretes most of the enzymes that digest proteins?
- Pepsin in the stomach
Proper function of what two accessory digestive organs is necessary for proper fat digestion by the small intestine?
Liver and pancreas
Why does diarrhea cause hypokalmia?
Diarrhea causes hypokalemia because absorption of water is necessary to create the osmotic gradient which drives potassium absorption. Water is not adequately absorbed by the intestinal mucosa (why diarrhea is watery). Those with diarrhea suffer from dehydration and hypokalemia.
Why do old folks have a problem with constipation?
GI tract activity declines, fewer digestive juices are produced, absorption is less efficient and peristalsis is slowed.
Why is colonoscopy recommended annually to individuals over 50?
Because colon cancer is the second leading cause of cancer deaths in males, develops initially from benign polyps, can be detected and removed by colonoscopy.
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