Midterm 3 Wilson Flashcards
What are the parts of the respiratory system?
a) Nose/Parnanasal sinuses
b) Pharynx
c) Larynx
d) Trachea
e) Bronchi
f) Lungs & Pleurae
What are the four processes of respiration?
1) Pulmonary Ventilation
2) External Respiration
3) Transport of Respiratory Gases
4) Internal Respiration
Which of the four processes of respiration are done by the respiratory system?
Pulmonary Ventilation and External Ventilation
What other system is involved?
Circulatory system
What are the two main functional divisions of the respiratory system?
1) Conducting Zone
2) Respiratory Zone
What is in the conducting zone?
Consists of a series of cavities and tubes that conduct air into the lungs (nose, pharynx, larynx, trachea, bronchi, bronchiole, and terminal bronchioles.
What is in the Respiratory zone?
Consists of the area where gas exchange occurs (respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
What are the two main anatomical divisions of the respiratory system?
1) Upper respiratory tract
2) Lower respiratory tract
What is in each of the two main anatomical divisions of the respiratory system?
- Upper respiratory tract (above vocal cords): Nose, Pharynx (throat), and Larynx (voicebox)
- Lower Respiratory tract (below vocal cords): Trachea (windpipe), bronci (airways), and Lungs & Pleurae (membranes)
What are the functions of the nose?
- airway
- warms, moistens, and filter incoming air
- receives olfactory stimuli
- serves as large, hollow resonating chambers to modify speech sounds
What are the divisions of the nose?
- External nose
2. Nasal Cavity
What are the main parts of the external nose?
Skin, nasal bones, & cartilage lined with mucous membrane (openings called external nares or nostrils)
- Root
- Bridge
- dorsum nasi
- apex
- nares (nostrils=bounded laterally by the flared alae)
Describe the pathway of air through the nose and nasal passageway and its parts.
- Nasal cavity divided by nasal septum; roof is ethmoid bone; floor is hard palate
- Air enters through nares into vestibule
- Conchae/meatus are projections/grooves on lateral walls that open to posterior nasal aperature
- The internal portion communicates with the paranasal sinuses and nasopharynx through the internal nares
What are nasal polyps?
Outgrowths of the mucous membranes which are usually found around the openings of the paranasal sinuses.
What is the nasal epithelium of the nasal passageway?
Contains olfactory receptors and mucus producing cells (secretes mucus)
What is the respiratory epithelium of the nasal passageway?
Pseudostratified columnar cells with cilia to move stuff (contains lysosome: antibacterial)
what is the function of Nasal epithelium?
Secretes mucus
what is the function of Nasal epithelium?
The olfactory epithelium is a layer of odor-sensitive cells located inside the depths of the nose. These cells react to odors as they enter the nose, sending signals to the olfactory bulb.
What is the function of the respiratory epithelium?
This lining acts as a barrier between the air coming into the body and the inner tissues of the respiratory mechanism, and it also serves to warm, clean and moisten the air in preparation for its arrival in the lungs.
What are the paranasal sinuses?
a group of four paired air-filled spaces that surround the nasal cavity
What is the function of the paranasal sinuses?
Lighten skull, warm & moisten air & resonate voice
What are the functions of the pharynx?
- Connects nasal cavity & mouth to larynx & esophagus
- Passageway for food and air
- resonating chamber for speech production
- tonsil (lymphatic tissue) in the walls protects entryway into body
What are the divisions of the pharynx?
- Nasopharynx
- Oropharynx
- Laryngopharynx
What is the role of the nasopharynx in respiration?
Passageway for air only
• Psuedostraified ciliated columnar epithelium (not used to move food) with goblet cells (produce mucus)
What is the role of the oropharynx in respiration?
Common passageway for food and air (abrasion from food: may layers)
• Stratified squamous epithelium
What is the role of the Laryngopharynx in respiration?
Common passageway for food & air; ends as esophagus inferiorly
• Stratified squamous epithelium
What are the functions of the larynx?
- Provide a patent (open) airway
- Act as a switching mechanism to route air and food into proper channels
- Voice production
What are the divisions of the larynx?
- Epiglottis
- Hyaline cartilages: thyroid, laryngeal prominence (adam’s apple), cricoid cartilage, arytenoid, cuneiform, corniculate
- Vocal Ligaments: Vocal cords, glottis, vestibular folds
Which anatomical divisions of the larynx play a role in swallowing?
Epiglottis
Which anatomical divisions of the larynx play a role in Voice production
Vocal ligaments
What role does the larynx play in swallowing?
During swallowing, larynx moves upward; epiglottis bends to cover glottis
What are the vocal cords?
Two pair of folds (superior and inferior)
What is the difference between the false and true cords?
False vocal cords: • Structure: mucous membranes • Function: holding breath True vocal cords: • Structure: Mucous membranes and elastic ligaments attached to cartilage • Function: set up sound waves
How do vocal cords play a role in speech production?
The vocal folds vibrate, producing sound as air rushes up from the lungs
How do various components of speech get produced (e.g. loudness, pitch)?
Pitch is controlled by tension on vocal folds
• Pulled tight produces higher pitch
• Male vocal folds are thicker and longer so vibrate more slowly producing a lower pitch
Whispering is forcing air through almost closed glottis—oral cavity alone forms speech.
What are the functions of the trachea?
- The cartilage rings keep the airway open
2. The cilia of the epithelium sweep debris away from the lungs and back to the throat to be swallowed.
What are the histological divisions of the trachea?
- Mucosa
- Submucosa
- Hyaline cartilage
- Adventitia
What is the role of each of the histological divisions?
- Mucosa: propel debris-laden mucus toward the pharynx
- Submucosa: secretes mucus
- Hyaline cartilage: allow stretch and movement inferiorly during inspiration and recoil during expiration.
- Adventitia: prevent trachea from collapsing
What is mucosa, submucosa, adventitia?
- Mucosa: goblet cell-containing pseudostratified epithelium (ciliated)
- Submucosa: CT layer deep to the mucosa, contains seromucous glands that help produce “sheets” within the trachea
- Adventitia: the outermost layer of connective tissue
What is a tracheostomy?
Incision in trachea below cricoid cartilage if larynx is obstructed
How does a tracheostomy compare to intubation?
Intubation is passing a tube from mouth or nose through larynx and trachea (no incision required)
What are the functions of the bronchi/bronchial tree?
- Conduction tubes
2. Respiratory zones: alveolar ducts where gas exchange takes place
What are the divisions of the bronchi / bronchial tree?
- Trachea
- primary bronchi
- secondary bronchi
- tertiary bronchi
- bronchioles
- terminal bronchioles
Describe how the histological features of the bronchi change as it goes from conducting to respiratory zone.
- In conduction zone: cartilage ring replaced by plates; epithelium thins, cilia sparse (decreases), smooth muscle increases (to control size of bronchioles); not as much cartilage
- In Respiratory zone: Alveoli simple squamous epithelium (Type 1 cells exchange; Type II secrete surfactant fluid) and capillaries = respiratory membrane
What are the cell types in the alveoli and what do they do?
- Type I alveolar cells
• Simple squamous cells where gas exchange occurs - Type II alveolar cells (septal cells)
• Free surface has microvilli
• Secrete alveolar fluid containing surfactant - Alveolar dust cells
• Wandering macrophages remove debris
What is respiratory distress syndrome?
a disorder of premature infants in chich the alveoli do not have sufficient surfactant to remain open.
What is surfactant?
Like detergent: it’s roles is to break up hydrogen bonds
What are the functions of the lungs?
Site of gas exchange
What are the divisions (anatomy) of the lungs?
- Pleurae (membranes)
- Gross anatomical features (hilium, cardiac notch, lobes, bronchopulmonary segments, lobules)
- Blood supply
What are the pleura of the lungs called and where is each?
- Visceral pleura: covers lungs
- Parietal pleura: lines ribcage & covers upper surface of diaphragm
- Pleural cavity: space between the visceral and parietal pleura where pleural fluid is made.
What is pleurisy?
Inflammation of membrane
describe the gross anatomical features of the lungs.
- Base, apex (cupula), costal surface, cardiac notch
- Oblique & horizontal fissure in right lung results in 3 lobes
- Oblique fissure only in left lung produces 2 lobes
Why is the right lung bigger?
Because the left lung has the cardiac notch to make room for the heart
What is the hilum?
An indentation on the mediastinal surface of each lung thru which pulmonary and systemic blood vessels, bronchi, lymphatic vessels, and nerves enter and leave the lungs.
Besides vessels, what else joins the lungs at the root?
bronchi, lymphatic vessels, and nerves enter and leave the lungs.
Why does the lung have two blood supplies and what are they?
- Pulmonary trunk: deoxygenated blood arrives through this from the right ventricle of the heart.
- Bronchial arteries: these branch off of the aorta to supply oxygenated blood to lung tissues
What is ventilation-perfusion coupling?
In the lungs vasoconstriction in response to hypoxia diverts pulmonary blood from poorly ventilated areas to well ventilated areas.
What are the transpulmonary / intrapulmonary / and intrapleural pressures and how does this deter lungs from collapsing?
Transpulmonary pressure (4mm hg) is the difference between intrapulmonary (760 mm hg) and intrapleural (756 mm hg) pressures.
Transpulomary pressure keeps air spaces for lung open. Lungs do not collapse because of negative pressure in the intrapleural space
When would lungs collapse?
When P_ip equalizes with the intrapulmonary (or atmospheric) pressure
What is pulmonary ventilation?
Breathing
As you inspire, the volume in the lungs increases and the pressure decreases. As you expire, the volume in the lungs decreases and the pressure increases.
As you inspire, the volume in the lungs increases and the pressure decreases. As you expire, the volume in the lungs decreases and the pressure increases.
How do the lungs change volume during inspiration / expiration
Inspiration: chest expands increasing volume
Expiration: Chest compresses decreasing volume
What muscles are involved in inspiration/exhalation?
Diaphragm and external intercostal muscles
What is quiet inspiration and how do pressures change during this process?
Quiet inspiration is the normal breathing (when at rest) you do without thinking about it. Intrathoracic pressure falls and 2-3 liters is inhaled.
What is the difference between quiet and forced inhalation?
Where quiet inhalation is the normal breathing when at rest, forced inhalation is the breathing that occurs when you are excercising or have some COPD.
Which muscles differ in quiet and forces inhalation?
- Quiet inspiration utilizes the diaphragm and external intercostal muscles.
- Forced inhalation uses the same muscles as well as accessory muscles (sternocleidomastoids, scaleness, and pectoralis minor)
What is quiet expiration and how do pressures change during this process?
Quiet expiration is a passive process with no muscle action. (inhalation, muscles relax)
Thoracic and intrapulmonary volume decreases and the pressure increases.
What is the difference between quiet and forced exhalation?
While quiet exhalation is a passive process, forced exhalation is an active procress
Which muscles differ in quiet and forced exhalation?
- Quiet exhalation uses no muscles
* Forces exhalation uses abdominal wall muscles
How do changes in pressure result in breathing?
- Alveolar pressure decreases & air rushes in (inhalation)
* Alveolar pressure increases & air rushes out (exhalation)
What 3 factors influence ventilation?
- Airway resistance
- Alveolar surface tension
- compliance
What does Airway Resistance mean?
Friction and drag reduce ventilation
What does Alveolar Surface Tension mean?
Water molecules at alveolar surface tend to stick together and prevent ventilation
What does Compliance mean?
Lung tissue is stretchy and distensible but may be diminished
How does airway resistance affect ventilation?
Resistance to airflow depends on the airway size. If the airway diameter is large then the resistance is low and air flows freely, if the airway diameter is small then the resistance is high and air flow is restricted.
Where is resistance greatest in the respiration pathway?
Medium-sized bronchi
How does an asthma attack affect resistance in the respiration pathway?
During an asthma attack, the bronchioles are constricted causing high resistance
What is alveolar surface tension?
The surface tension that exists between water molecules (H bonds) inside lung
What is Surfactant?
A detergent like compound to reduce surface tension
Which cells produce surfactant?
Type II alveolar cells
What is respiratory distress syndrome?
A disorder of premature infants in which the alveoli do not have sufficient surfactant to remain open
What is lung compliance?
Ease with which lungs & chest wall expand (depends upon elasticity of lungs & surface tension)
What disorders can reduce compliance?
- Tuberculosis
- Pulmonary edema
- paralysis
What are the 4 types of respiratory volumes?
- Tidal Volume
- Inspiratory Reserve
- Expiratory Reserve
- Residual Volume
What does Tidal Volume measure?
amount of air moved during quiet breathing (500 mL)
What does Inspiratory reserve volume measure?
The amount of air that can be inspired forcibly beyond the tidal volume (3100 mL)
What does Expiratory Reserve volume measure?
The amount of air that can be expired forcibly after a normal tidal volume expiration (1200 mL)
What does Residual volume measure?
Permanently trapped air in the lungs; amount of air left in lungs even after the most strenuous expiration (1200mL)
What is the difference between vital and total lung capacity?
These are the sums of the other volumes
• Vital capacity is the sum of Inspiratory reserve volume, tidal volume, and expiratory reserve volume (4800 mL)
• Total lung capacity is the sum of all 4 of the respiratory volumes (6000 mL)
What is the minute ventilation rate?
Amount of air moved in a minute
How does one measure respiratory volumes?
With a spirometor
How can breathing rates change and the names for the changes?
- Apnea: breath holding (sleep apnea)
- Dyspnea: painful or difficult breathing
- Tachypnea: rapid breathing rate
- Costal Breathing: (uses intercostal & extracostal muscles) need for increased ventilation (as with exercise)
- Diaphragmatic Breathing: usual mode of operation to move air by contracting and relaxing the diaphragm to change the lung volume
- Modified Respiratory Movements: Used to express emotions and to clear air passageways
What are some non-respiratory changes in ventilation?
- Cough
- Sneeze
- Crying
- Laughing
- Hiccups
- Yawn
What are the three steps in gas exchange and where does each occur?
- Ventilation:
- External (pulmonary) respiration: in lungs
- Internal (tissue) respiraton: in tissues
What three factors determine the movement of gases in our bodies?
- Composition of air and partial pressure of gasses in atmosphere, in alveoli air, and in expired air (Dalton’s law of partial pressure)
- Gas’s solubility (Henry’s Law)
- Hemoglobin structure and affinity to O2 and CO2
What is Dalton’s law and how does this determine how gases move in our bodies?
- Air is composed of 21% O2, 79% N2, and .04% CO2
- Each gas in a mixture of gases exerts its own pressure=partial pressure (p)
- Total pressure is sum of all partial pressures
Partial pressure gradients (differences) exist between different areas of the body that will promote the movement of gases
How do gradients vary across the body?
the Alveoli have a higher pressure gradient of O2 and lower pressure gradient of CO2. Where as tissues have a lower pressure gradient of O2 and higher CO2 pressure gradient.
How does the gradient variations across the body drive internal and external respiration processes?
allows tissues to receive the O2 they need while getting rid of CO2
What is Henry’s law?
States that the quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and it’s solubility coefficient.
How does Henry’s law determine how gases move in the body?
Gases with a higher concentration will move faster than ones with lower concentration
What is a hyperbaric chamber and how does that increase gas solubility?
It’s a chamber that contains O2 gas at pressures higher than 1 atm are used to force greater-than-normal amount of O2 in the blood. This increases solubility as the concentration of O2 is higher.
what are four factors that affect respiration rate of diffusion?
- Concentration gradient
- Surface area
- Diffusion difference
- Molecular weight & solubility
How can each of the four factors that affect respiration rate of diffusion change?
- Concentration gradient: the greater the difference, the faster the rate of diffusion
- Surface area: disease or injury that decrease that surface area
- Diffusion difference: build up of fluid in the lungs increases the diffusion distance
- Molecular weight & solubility: Low Po2 will usually be a problem before High Pco2 in the blood
What is ventilation/perfusion coupling?
In the lungs, vasoconstriction in response to hypoxia diverts pulmonary blood from poorly ventilated areas to well ventilated areas.
How does ventilation/perfusion coupling keep our body in homeostasis?
the changing diameter of locar bronchioles and arterioles synchornizes alveolar ventilation and pulmonary perfusion
• Po2 controls perfusion by changing arteriolar diameter
• Pco2 controls ventilation by changing bronchiolar diameter
How does Hemoglobin play a role in gas exchange?
O2 (98%) binds to the heme to be carried from the lungs to the tissues and the globin carries some CO2 (20%)
Which gases does hemoglobin play a role in?
O2 and CO2
How does Oxygen saturation change with partial pressure?
It increases as partial pressure increases
What are some differences between an exercising and a resting muscle, and why do each get different amounts of oxygen?
Resting muscles have more partial pressure than exercising muscles so therefore have less saturation..
Know three ways carbon dioxide is transported in the blood.
- Dissolved in plasma (7%)
- Combined with globin part of Hb molecule forming carbaminohemoglobin (23%)
- As part of bicarbonate ion (70%)
How does this differ from Oxygen?
Oxygen is carried on heme (98%)
Why is carbon monoxide poisoning bad?
it binds strongly to iron in hemoglobin. Once it attaches, it is very difficult to release. It sticks to you hemoglobin and takes up all of the oxygen bind sites and causes your blood to lose it’s abliity to transport oxygen.
How does bicarbonate regulate pH of blood?
HCO3 combines with H+ to remove excess H+ or HCO3 dissociates by releasing H+ when not enough H+
where are the respiratory centers in the central nervous system?
- Medullary center
* Pontine Center
What are the 2 medullary centers and what does each do?
- Dorsal respiratory group: sensory inputs from periphery
* Ventral respiratory group: motor rhythm generation (exciting breathing muscles)
What is the center in the pons and what role does it play in respiration?
Pontine Center: smooth respiratory movement; modifiers for breathing (indirect; fine tunes)
What are the two factors that regulate respiration?
- Higher brain centers (voluntary control)
* Chemical factors (involuntary control)
What higher brain regions can regulate respiration ?
(cortical influences) Hypothalamus & primary motor cortex
What stimuli overrides voluntary control of breathing?
Increased H+ and CO2
What is the pulmonary irritant reflex?
Reflex constriction of air passages (cough, sneeze, etc) due to an irritant.
What is the Inflation reflex?
Stretch receptors, if not activated, start breathing.
What are the chemical factors involved in regulating breathing?
- Central chemoreceptors in the medulla
* Peripheral chemoreceptors
Which is a more potent stimulus – low Oxygen or high CO2?
High CO2
Where are the central chemoreceptors and peripheral receptors?
- Central chemoreceptors: in medulla
* Peripheral chemoreceptors: wall of aorta and walls of common carotid arteries
What is hypercapnia?
Slight increase in pCO2 is noticed
What is Hyperventilation?
Excessive ventilation, characterized by low Pco2 and alkalosis
How does a negative feedback system regulate breathing?
hypoventilation
What is hypoventilation?
Under breathing
What are two factors that increase and decrease ventilation?
- Limbic system
* Proprioceptor activity
What are some ways respiration can be adjusted?
- Exercise
- High altitude
- Aging
What changes occur during exercise?
As blood flow increases with a lower O2 and higher CO2 content, the amount passing thru the lung increases and is matched by increased ventilation and oxygen diffusion capacity as more pulmonary capillaries open.
What are 3 neural factors involved in exercise-respiration?
- Psychological stimuli
- Cortical Motor activation
- proprioceptors
What changes occur when one smokes?
Easily “winded” with moderate exercise (less ventilation, less perfusion)
How does this affect the lungs?
- Nicotine constricts terminal bronchioles (less air in alveoli
- Carbon monoxide in smoke binds to hemoglobin
- Irritants in smoke cause excess mucus secretion
- Irritants inhibit movements of cilia (sometimes killing cells)
- In time, destroys elastic fibers (reduce compliancy) in lungs and leads to emphysema
How does high altitude lead to changes in respiration?
As you get higher there is less oxygen, as a result ventilation increases as the brain attempts to restore gas exchange to previous levels.
What are some short and long term effects of high altitude?
- short term effects: acute mountain sickness (nausea, headaches, shortness of breath, dizziness)
- Long term effects: will lead to acclimatization and EPO production (increased RBC’s)
What is acclimatization?
Adaptive response
What happens to EPO levels?
they increase
How does aging change respiration capabilities?
- Respiratory tissues and chest wall become more rigid
- Vital capacity decreases to 35% by age 70
- Decreases in macrophage activity
- Diminished ciliary action
- Decrease in blood levels of O2
- Result is age-related susceptibility to pneumonia or bronchitis
What are the homeostatic imbalances related to the respiratory system and what part of the respiratory system is affected?
- • Pneumothorax - membranes
- Asthma – conducting zone
- Hypoxia – respiratory zone
- COPD – respiratory zone
- Emphysema – respiratory zone
- Chronic bronchitis – conducting zone
- Bronchogenic carcinoma – conducting zone
- Pneumonia – respiratory zone
- Coryza (common cold) – conducting zone
- Tuberculosis – membranes
- Pulmonary edema – respiratory zone
- Cystic fibrosis – conducting zone
- Asbestos – membranes
- Sudden infant death syndrome (SIDS) – unknown
What is the difference between the effects of bronchitis and emphysema on the alveoli?
- Emphysema: distinguished by permanent enlargement of the alveoli, accompanied by destructionof the alveolar walls.
- Bronchitis: chronic production of excessive mucus inpairs ventilation and gas exchange
What are the functional segments of the digestive system?
- Mouth/pharynx
- Esophagus
- Stomach
- Small intestines
- Large instestines
What are the accessory structures of the digestive system?
- Teeth
- Toungue
- Salivary glands
- Liver
- Gallbladder
- pancreas
What are the anatomical features responsible for some of the digestive system functions?
- Mouth: bite, chew, swallow, limited lipid & carb digestion
- Pharynx & esophagus: transport
- Stomach: mechanical disruption: absorption of water & alcohol, protein & lipid digestion
- Small Intestines: most chemical & mechanical digestion & absorption
- Large intestines: absorb electrolytes & vitamins (B and K)
- Rectum & anus: defecation
Describe the stimuli and controls of digestive activity.
- Mechanical & chemical stimuli (internal to GI Tract)
• Stretch, osmolarity, pH sensors monitor conditions that promote reflexive activity that:
o Activate glands/hormones
o Stimulate smooth muscle (will promote short reflexes; local) - Extrinsic control: autonomic nervous system
• Enteric nervous system controls short reflexes; long reflexes controlled by extrinsic signals
What are the 6 processes that occur in the digestive system and define them:
• Ingestion: taking food into the mouth (eating
• Secretion: the release, by cells within the walls of the GI tract and accessory organs, of water, acid, buffers, and enzymes into the lumen of the tract
• Mixing/propulsion: result from the alternating contraction and relaxation of the smooth muscle
• Digestion: breakdown of food
o Mechanical: consists of movements (smooth muscle contraction) of the GI tract that aid in chemical digestion
o Chemical: is a series of catabolic (hydrolysis) reactions that break down large carbohydrate, lipid, and protein food molecules into smaller molecules that are usable by body cells
• Absorption: the passage of end products of digestion from the GI tract into blood or lymph for distribution to cells
• Defecation: emptying of the rectum, eliminating indigestible substances from the GI tract
What are the membranes of the digestive system called?
Peritoneum
What is mesentery?
Double layer of membrane; back to back
What is peritonitis?
Inflammation of the peritoneum
What are omenta?
Tethers stomach to other digestive organs
Name at least three omenta
- Greater omentum
- Mesentery
- Lesser omentum
What are some common histological features of the digestive tract?
Walls of the alimentary canal have the same layers
How many layers are there in the digestive tract?
4`
What are the 4 layers in the digestive tract?
- Mucosal layer
- Submucosa:
- Muscularis externa:
- Serosa: visceral peritoneum
What is the basic feature of the Mucosa layer?
Has 3 layers:
Epithelium
• Stratified squamous (in mouth, esophagus, & anus) simple columnar in the rest.
Lamina Propria
• Thin layer of loose CT, contains BV and lymphatic tissue
Muscularis mucosae
• Thin layer of smooth muscle
What is the basic feature of the submucosa Layer?
Loose connective tissue (areolar CT)
Meissner’s plexus (submucousal nerve plexus (enternic nervous system)
• Parasympathetic innervation
What is the basic feature of the muscularis externa layer?
- Skeletal muscle = voluntary control
* Smooth muscle = involuntary control
What is the basic feature of the serosa layer?
- Areolar CT
- Extension of visceral peritoneum
- Covers all organs and walls of cavities not open to the outside of the body
- Secretes slippery fluid
- Consists of connective tissue covered with simple squamous epithelium
In the mucosal layer, where does the type of epithelial cell changes and why
The mouth, esophagus, and anus have stratified squamous epithelium to protect against abrasion. The rest of the tube is simple columnar epithelium rich in mucus-secreting cells.
What is adventitia and where is it found?
ordinary fibrous CT. Found in esophagus and retroperitoneal organs (on side facing the peritoneal cavity)
In which layers of the digestive tract does the enteric nervous system appear?
Submucosa and Muscularis Externa
What are the anatomical features of the mouth?
- Lips (labia) and cheeks
- Vestibule
- Oral cavity proper
What function does the mouth play in digestion?
- Ingestion
- Digestion
- Propulsion
What are the anatomical features of the pharyngeal?
- Two skeletal muscles
- Palatoglossal muscle (superior arch)
- Palatopharyngeal muscle
What function does the pharyngeal arches play in digestion?
- Anchors soft palate to tongue
* Posterior limit of mouth
What are the anatomical features of the tongue?
- Muscle of tongue is attached to hyoid, mandible, hard palate and styloid process
- Papillae are the bumps—taste buds are protected by being on the sides of papillae
What function does the tongue play in digestion?
- Mixes food, grips food and
- repositions between teeth,
- initiatiates swallowing
What are the 3 different salivary glands?
- Parotid gland
- Submandibular gland
- Sublingual gland
What function does saliva play in digestion?
Lubricates and dissolves food; also starts the chemical digestion of carbohydrates
What are some of saliva’s chemical features?
• 99.5% water and • 0.5% solutes such as o salts o dissolved gases o various organic substances o enzymes.
What is a homeostatic imbalance that affects the parotid gland?
Myxovirus
What are the anatomical features of teeth?
- Crown
- Neck
- Roots
- Pulp cavity
- Enamel
- Dentin
- Cementum
What function do teeth play in digestion?
Mechanical digestion (masticate food)
What is primary and secondary dentition?
- Primary Dentition: Deciduous Teeth (baby teeth)
* Secondary Dentition: Permanent teeth
What are the anatomical features of the pharynx?
- Funnel-shaped tube extending from internal nares to the esophagus and larynx
- Skeletal muscle lined by mucous membrane
What function does the pharynx play in digestion?
Passageway for food
What are the anatomical features of the esophagus?
- Collapsed muscular tube
- In front of vertebrae
- Posterior to trachea
- Posterior to the heart
What function does the esophagus play in digestion?
to secrete mucus and transport food to the stomach.
What is a hiatal hernia?
• Pierces the diaphragm at hiatus
What is GERD?
Gastroesophageal Reflex Disease
What is meant by a “physiological sphincters” in the cardiac orifice?
Also called cardiac sphincter; acts as sphincter but only structural evidence of this sphincter is a slight thickening of the circular smooth muscle at that point.
What are the anatomical features of the stomach?
J-shaped enlargement of the GI tract that begins at the bottom of the esophagus and ends at the pyloric sphincter
What function does the stomach play in digestion?
- Serves as a mixing and holding area for food
- Begins the digestion of proteins
- Continues the digestion of triglycerides,
- Converting a bolus to a liquid called chyme
- Can also absorb some substances.
What is a bolus?
Mass of food prepared by the mouth for swallowing
What is Chyme?
Creamy paste that food is converted into
What is Rugae?
Folds that flatten when filled with bolus;
What type of epithelial cells line the stomach?
Simple columnar
What are some other histological features of the stomach layers?
• Mucosa mad of simple columnar cells (mucous surface cells)
• Gastric pits
• Gastric glands (consist of 3 types of exocrine glands)
o Mucuous neck cells (secrete mucus)
o Chief or zymogenic cells (secrete pepsinogen and gastric lipase)
o Parietal or oxyntic cells (secrete HCl)
Gastric glands also contain enteroendocrine cells (produce hormone gastrin)
what are the four type of gland cells in the gastric pits?
- Mucous neck cells
- Parietal cells
- Chief cells
- Enteroendocrine cells
What does the mucous neck cells do?
Acidic mucous (function ?)
What does the parietal cells do?
secrete HCl and intrinsic factor; Function: acid increases pepsin and breaks down food and bacteria)
What does the chief cells do?
Secrete pepsinogen: activated by HCl to form pepsin to break down proteins and lipase for fat breakdown
What does the enteroendocrine cells do?
Secrete several paracrines and hormones (includes G cell)
What are the steps in digestion up to the stomach?
- Ingestion
- What goes in the mouth
- After masitication, the bolus is swallowed = deglutition
- After swallowing, the stomach begins Mechanical Digestion
- After digestion, the stomach begins some (limited) absorption
- After stomach, move on to the small intestine where most absorption takes place
What happens in the mouth?
- Mechanical digestion (mastication)
a. Breaks into pieces
b. Mixes with saliva so it forms a bolus - Chemical digestion
a. amylase
• Begins starch digestion at pH of 6.5or 7.0 found in mouth
• When bolus & enzyme hit the pH 2.5 gastric juices hydrolysis ceases
b. lingual lipase
• Secreted by glands in tongue
• Begins breakdown of triglycerides into fatty acids and glycerol
What is mastication?
chewing
What happens in the pharynx?
- Voluntary phase: tongue pushes food to back of oral cavity
- involuntary phase: pharyngeal stage
• Breathing stops & airways are closed
• Soft palate & uvula are lifted to close off nasopharynx
• Vocal cords close
• Epiglottis is bent over airways as larynx is lifted
What is deglutition?
The bolus is swallowed
What is the difference between the voluntary and involuntary phases of swallowing?
- Voluntary (or buccal phase) occurs in the mouth and is voluntary.
- Involuntary (or pharyngeal-esophogeal phase) is controlled by the swallowing center located in the brainstem (medulla and lower pons)
What happens in the esophagus?
Involuntary phase (esophagus stage)
• Peristalsis moves food by pressure gradients: circular fibers behind bolusand longitudinal fibers in front of bolus shorten the distance of travel
• Travel time is 4-8 sec for solids and 1 sec for liquids
• Lower sphincter relaxes as food approaches
What part of the stomach is involved in each type of mechanical digestion?
- Gentle mixing waves: body of stomach
- More vigorous waves: pyloric region
- Intense waves: near pylorus
What is the stomach’s role in chemical digestion?
- Digest proteins
- Digest fats
- Cells that produce HCl (Parietal cells)
What is the role of HCl?
- Denatures (unfolds) protein molecules
* Transforms pepsinogen into pepsin
What is the role of pepsin?
breaks peptides bonds between certain amino acids
What is the role gastric lipase?
Splits the triglycerides in milk fat
• Most effective at pH 5 to 6 (infant stomach)
What are the three phases of digestion that regulates gastric juice secretion?
- Cephalic phase
- Gastric phase
- Intestinal phase
What is the stomach’s role in absorption?
It begins some limited absorption; some water, electrolytes, certain drugs (especially aspirin), lipid based hormones, and alcohol through the lining
How does the stomach empty and into what?
Gastric emptying is a result of peristalsis; empties into the small intestine
What is vomiting?
also callled emesis; reflex caused if irritants or toxins are present
What is the general anatomy of the small intestine ( including 3 main parts and the sphincters at either end.)
- The small intestine extends from the pyloric sphincter to the ileocecal sphincter.
- The small intestine is divided into the duodenum, jejunum, and ileum.
What are plicae circularis?
Permanent ½ inch tall folds that contain part of submucosal layer
What are Villi?
1 mm tall on surface of plicae circolarus that contains vascular capillaries and lacteals (lymphatic capillaries)
What are Microvilli?
Tiny projections on the surface of each cell of villus
Why does the presence of villi and microvilli increase surface area?
There are vast numbers of each
What is the brushborder?
Microvilli
Why is microvilli named the brushborder?
because of their fuzzy appearance
Describe the histology of the small intestine.
- Made up of 4 layers
- Has lumen
- Circular fold
- Villi
How are the mucosa and submucosa specialized?
- Epithelium has absorptive cells w/ tight junctions and goblet (hormone) cells
- Epithelium has pits with intestinal crypts andenteroendocrince cells, T cells, Paneth cells
- Submucosa made of Areolar CT: contains aggregated lymph tissue called Peyer’s patches
What are intestinal crypts?
Glands found in the epithelium lining of the small intestine and colon; contains gobblet cells and enterocytes
What are Enteroendocrine cells?
Specialized endocrine cells of the GI tract and pancreas that produce gastrointestinal hormones or peptides.
What are Intraepithelial lymphocytes?
Lymphocytes found in the mucosal lining of the GI tract
Name the cells of the small intestine
- Absorptive cell
- Goblet cell
- Enteroendocrine
- Paneth cells
What does the absorptive cells do?
Digests and absorbs nutrients
What does the goblet cells do?
Secretes mucus
What does the enteroendocrine cells do?
Secretes the hormones secretin, cholecystokinin, or GIP (gastric inhibitory peptide)
What does the Paneth cells do?
Secretes lysozyme kills bacteria (antibacterial)
what are the main anatomical features of the liver?
- Heaviest gland
- Second largest organ (after skin)
- Divisible into left and right lobes, separated by falciform ligament
- Associated with right lobe are the caudate and quadrate lobes
What are the main anatomical features of the gallbladder?
Sac located in a depression on the posterior surface of liver
What is the liver’s role in digestion?
- Carbohydrate, lipid, and protein metabolism
- Removal of drugs and hormones from the blood
- Excretion of bilirubin
- Synthesis of bile salts (made by liver cells)
- Storage of vitamins and minerals
- Phagocytosis
- Activation of vitamin D
What are some histological features of the liver?
- Hepatocytes arranged in lobules
- Sinusoids in between hepatocytes are blood-filled spaces
- Kupffer cells phagocytize microbes & foreign matter
What are hepatocytes?
Liver cells
What are Sinusoids?
blood filled spaces
What are Central veins?
Vein running in the longitudinal axis of the lobule
What are Kupffer cells?
Cells that phagocytize microbes & foreign matter (break down old RBC’s)
What are Lobules?
Sesame seed-sized structural and functional units
Where is bile produced?
Hepatocytes
Where is bile headed?
the gallbladder for storage til needed
What is a bile canaliculi?
Tiny canals
What is the pathway of the bile once itis produced?
- Bile passes into bile canaliculi
- To bile
- To common hepatic duct
- To cystic duct
- to common bile duct
- Entering hepatopancreatic ampulla
What are some histological features of the gallbladder?
- Simple columnar epithelium
- No submucosa
- Three layers of smooth muscle
- Serosa or visceral peritoneum
What is the gallbladder’s role?
Bile storage that is not immediately needed for digestion and concentrates it (10-20 x’s than in liver)
What homeostatic imbalances can becaused when cystic duct (or hepatic / bile duct) is blocked?
Gallstones or jaundice
what are the general vessels associated with blood supply to the liver (7)?
- Hepatic artery
- Hepatic portal vein
- Liver sinusoids
- Central vein
- Hepatic vein
- Inferior vena cava
- Right atrium of heart
What are some general anatomical features of the pancreas?
- 5” long by 1” thick
- Head close to curve in C-shaped duodenum
- Main duct for pancreatic juices joins common bile duct from liver
- Sphincter of Oddi on major duodenal papilla
What is the name of the sphincter that controls its release into the small intestine?
Sphincter of Oddi
What is the pathway of the liver and pancreas ducts joining to form the major input into the small intestine?
- Right and left hepatic duct join into
- Common hepatic duct from liver
- Cystic duct joins common hepatic duct into
- Common bile duct
- Pancreatic duct joins common bile duct into
- Duodenum
What are some histological features of the pancreas:
- Acini-dark clusters (99% of gland; exocrine function)
* Islets of Langerhans (1% of gland; pale staining cells; endocrine function)
What are acini?
Clusters of secretory acinar cells surrounding ducts
What do acini produce?
Pancreatic juice
What are Islets of Langerhans?
Mini endocrine glands that produce insulin and glucagon hormones
What is in pancreatic juice?
Water, enzymes, and sodium bicarbonate (neutralizes highly acidic chyme)
How does pancreatic juice play a role in digestion?
Helps neutralize acid chyme entering the duodenum
What are the names for some of the digestive enzymes
- Pancreatic amylase (breaks down sugars)
- Pancreatic lipase (breaks down lipids)
- Proteases (breaks down protein)
- Ribonuclease (breaks down nucleic acids)
- Deoxyribonuclease
Once the stomach empties into the duodenum, what prohibits further filling of this area?
Stretch and chemoreceptors
Why is it important to limit the amount of material in the duodenum?
To prevent overfilling and over stretching
What is trophology?
Food ordering
What are the two processes that must occur in the small intestine for digestion.
Mechanical and chemical
What is the mechanisms for the mechanical process of digestion in the small intestine?
- Peristalsis
* Segmentation
What is the mechanisms for the chemical process of digestion in the small intestine?
- Intestinal juices
- Bile
- Pancreatic juices
- Bicarbonate
What is segementation?
A localized contraction in areas containing food (major movement in small intestine)
What controls the rhythm of segementation?
Peristalsis
A special type of peristalsis occurs in the small intestine. What is it called?
Segmentation/weak peristalsis
What kind of enzymes are secreted by the pit cells and are found in intestinal juices?
• Brush border enzymes: break down carbs and proteins
o Aminopeptidase
o Carboxypeptidase
o Dipeptidase
What kind of foodstuffs do the enzymes secreted by the pit cells break down?
Carbs and proteins
What is lactose intolerance?
Deficiency of intestinal lactase causing inability to break down lactose sugar commonly found in milk
What is bile?
Yellow-green, alkaline solution containing pigments, salts, cholesterol, triglycerides, phospholipids, and electrolytes
What in bile is involved in food digestion?
The salts and phospholipids
What is emulsification?
Break down of large fat globules into smaller uniformly distributed particles
Are all parts of the bile recycled? If not, which ones get defecated?
No. bile salts are recycled, rest defecated
What two hormones control the release of bile and pancreatic juices?
Cholecystokinin and secretin
What are the enzymes in pancreatic juices that aid in food digestion?
- Pancreatic amylase
- Pancreatic lipase
- Proteases
- Ribonuclease
- Deoxyribonuclease
Where else besides pancreatic juices are enzymes involved in food digestion
Small intestine
What is the role of bicarbonate and where does it come from?
Bicarbonate neutralizes stomach acid and comes from pancreatic juice, bile
Once foods are digested, where are they absorbed?
Most in duodenum, but can occur anywhere in small intestine
What are the mechanisms by which nutrients are absorbed
- Diffusion
- Facilitated diffusion
- Osmosis
- Active transport
What is the role of the tight junction between the epithelial cells?
Everything has to be invited into the bloodstream. Materials must pass thru the epithelial cells & into the interstitial fluid abutting their basolateral membranes to enter the blood capillaries.
Does absorption always require energy?
No. only polar substances require ATP
What is the role of the ileum?
Reclaims bile salts
Where do the nutrients go once they are absorbed?
Into the blood and lymph
What are the parts of the large intestine?
• Ascending colon • Transverse colon • Descending colon • Sigmoid colon o Cecum o Appendix o Colon o Rectum o Anal canal • External anal sphincter • Internal anal sphincter
Which parts of the large intestine are retroperitoneal?
- Ascending colon
- Descending colon
- rectum
What are teniae coli?
Smooth muscle
What are Haustra?
Pocket like sacs
What are Epiploic appendages?
Small fat-filled pouches of visceral peritoneum (function unkown)
What are some histological features of the large intestine.
- Mucosa: simple columnar
- Thick with crypts (intestinal crypts)
- Goblet cells produce mucus (eases passage of feces)
- No villi
How does the histological features of the large intestine differ from the small intestine?
- SI has villi; LI doesn’t
- SI has glands in submucosa; not LI
- SI has lympatic nodes in submucosa; not LI
What are the two sphincters that control feces release and how are each controlled?
- External anal sphincter (voluntary)
* Internal anal sphincter (involuntary)
What are the roles of bacteria flora in the large intestine?
- Metabolize some host-derived molecules (heparine, mucin, hyaluronic acid)
- Ferment indigestible carbohydrates
- Release irritating acids and a mixture of gases
- Makes vitamin K and B
What are the digestive processes that occur in the large intestine?
– Enteric bacteria will digest nutrients and Vitamin K and B will be absorbed
– Water will be reabsorbed (and some Na and Cl)
What kind of mechanical processes occur in the large intestine?
- Peristalsis
- Haustral churning
- Mass peristalsis
What kind of chemical processes occur in the large intestine?
• Bacteria ferment breakdown
What is haustral churning?
Relaxed pouches are filled from below by muscular contractions (elevator)
What is Mass peristalsis?
Long, slow, powerful contractions that move over large areas of the colon
What is Gastroilial reflex?
When stomach is full, gastrin hormone relaxes ileocecal sphincter so small intertine will empty and make room
What is Gastrocolic reflex?
When stomach fills, a strong peristaltic wave moves contents of transverse colon into rectum
What is role of bacteria in large intestine chemical digestion?
• Bacteria ferment
– undigested carbohydrates into carbon dioxide & methane gas
– undigested proteins into simpler substances (indoles)—-odor
– turn bilirubin into simpler substances that produce color
• Bacteria produce vitamin K and B in colon
What is one possible role of the appendix?
immune function
What is inflammation of the appendix called?
appendicitis
What can a ruptured appendix cause?
Can result in gangrene or peritonitis
What is absorbed in the large intestine?
- Some electrolytes (Na+ and Cl-)
* H2O
What is feces?
- dead epithelial celss
- undigested food such as cellulose
- bacteria (live and dead)
How is defecation controlled?
by voluntary contractions of the diaphragm and abdominal muscles.
What is diarrhea?
chyme passes too quickly through intestine (H2O not reabsorbed)
What is Constipation?
Decreased intestinal motility (too much water is reabsorbed)
How does dietary fiber affect digestion?
Affects the speed of food passage through GI tract
• insoluble fiber (woody parts of plants; wheat bran, veggie skins)
• soluble fiber (gel like constistency; beans, oats, citrus white parts, apples)
What is a colonoscopy?
Visual examination of the lining of the colon using an elongated, flexible, fiberoptic endoscope
What is an occult blood test?
Test to screen for colorectal cancer
What happens to our digestive system as we age?
– decreased secretory mechanisms
– decreased motility
– loss of strength & tone of muscular tissue
– changes in neurosensory feedback
– diminished response to pain & internal stimuli
What are some disorders of the mouth and teeth?
- Dental caries (tooth decay)
* Periodontal diseases
What are peptic ulcers?
Crater-like lesions that develop in the mucous membraneof the GI tract in areas exposed to gastric juice.
What are diverticula?
Saclike out pouchings of the wall of the colon in places where the muscularis has becom weak
What are Diverticulitis?
Inflammation within the diverticula
What are Diverticulosis?
The development of diverticula
What is hepatitis?
inflammation of the liver
What is anorexia nervosa?
Chronic disorder characterized by self-induced weight loss, body-image and other perceptual disturbances, and physiologic changes that result from nutritional depletion.
What is filtration?
Kidneys filter fluid from the blood
What is Reabsorption?
Kidneys allow needed substances to stay
What is Secretion?
Cell product that is transported to the exterior of the cell
What is excretion?
Elimination of waste products from the body
What are the parts of the urinary system?
- 2 kidneys
- 2 ureters
- Urinary bladder
- Urethra
What is the function of the urinary system?
Filter the blood and return most of the water and solutes to the bloodstream
What is nephrology?
Study of kidneys
What is Urology?
Study and treatment of the urinary tract
What are the functions of the kidney?
- Regulation of
• Blood ionic composition: Na+, K+, Ca2+, Cl- and phosphate ions
• Blood pH, osmolarity, & glucose
• Blood volume (how much urine to make)
• Conservation or elimination of water (hormones)
• Blood pressure (secreting the enzyme renin, adjusting renal resistance) - release of erythropoietin (increase #RBC)
- Excretion of wastes & foreign substances
- final step to converting Vitamin D into its final form
- gluconeogenesis (make new glucose) during fasting
What hormones are released by the kidney?
- Erythropoietin
* Calcitriol
Describe the external anatomy of the kidney.
• The paired kidneys are retroperitoneal kidney-bean-shaped organ
• 4-5 in long, 2-3 in wide,
1 in thick organs
• Three layers of tissue surround each kidney:
Why is the right kidney slightly lower than the left?
Because it’s crowded by the liver
What are the three layers of connective tissue that surround the kidney?
- Innermost fibrous capsule (thin, prevents infection)
- Adipose capsule (perirenal capsule, cushioning)
- Outer renal fascia (CT dense, connects to nearby structures)
what is hydronephrosis?
urine backup
what is renal ptosis
kidney drops inferiorly (can happen if lose weight quickly)
Describe the internal anatomy of the kidney.
- Has 3 regions
- Papillae
- Columns
- Calyces
- Pyramids
What are the three main regions of the kidney?
- Cortex (outer shell)
- Medulla (internal tissue, cone shaped-renal pyramids)
- Pelvis (deep, collecting area for urine produced; cavity = drainage system)
What is the papillae of the kidney?
Apex of pyramid
What is the columns of the kidney?
Where cortex comes into medulla
What is the calyces of the kidney?
Collecting area
What is the pyramids of the kidney?
Cone shape of medulla
What makes up the parenchyma of the kidney?
- Renal cortex
* Renal medulla
what makes up the drainage system of the kidney?
- Minor calyces (cuplike structure collect urine )
* Minor & major calyces (empty into the renal pelvis)
What is pyelitis?
Inflammaton of renal pelvis & calyx
What is Pyleonephritis?
Inflammation of entire kidney
What are the capillary branches of the kidney?
- Peritubular capillary
- Glomerular capillaries
- Vasa recta
What is the nerve supply to the kidney called?
renal plexus
What part of the autonomic nervous system is mostly responsible for altering kidney blood flow and renal resistance?
Sympathetic
What is a nephron?
Functional unit of the kidney
What are the main structural components of a nephron?
- a glomerulus where fluid is filtered
2. a renal tubule into which the filtered fluid passes
What is the function of a nephron?
- glomerular filteration
- tubular reabsorption
- tubular secretion
How is urine formed?
- Plasma moves into the glomerular capsule (fluid called filtrate)
- Filtrate moves along the tubules (fluid is tubular fluid)
- Water and molecules not reabsorbed into blood is secreted into the tubular fluid
- Fluid moves into the collecting duct (urine)
What is the difference between filtrate, tubular fluid and urine and where is each found in the kidney nephron system?
- Filtrate from plasma that moves into the glomerular capsule
- Tubular fluid is filtrate after most water and molecules have been removed and is in the renal tubule
- Urine is the tubular fluid that collects into the collecting ducts.
What are the parts of the nephron and the role of each?
- Renal corpuscle: filteration of plasma into filtrate
- Nephron loop: processes filtrate
- Collecting duct: receives filtrate and deliver urine into minor calyces
What are the differences between cortical and juxtamedullary nephrons?
- Cortical Nephron:
• Short loop of Henle
• Glomerulus further from the corticomedullary junction
• Efferent arteriole supplies peritubular capillaries - Juxtamedullary Nephron:
• Has long loop of Henle
• Glomerulus closer to the corticomedullary junction
• Efferent arteriole supplies vasa recta
Which type of capillary bed serves each (cortical and juxtamedullary nephrons)?
- Cortical Nephron: peritubular capillaries
* Juxtamedullary Nephron: vasa recta
What are the three types of blood vessels around the nephrons called
- Glomerulus
- Peritubular capillaries
- Vasa recta
What is the role of the glomerulus?
Produces filtrate from blood
What is the role of the peritubular capillaries?
Reclaim most of filtrate
What is the role of the Vasa recta?
Supplies nutrients to medulla and concentrate urine
What are the layers of the Bowman’s capsule?
- Parietal layer
* Visceral layer
What are podocytes?
Cover capillaries to form visceral layer
What are glomerular capillaries?
Arise from afferent arteriole & form a ball before emptying into efferent arteriole
What is the capsular space and why is it important in filtrate formation?
It’s the space between the 2 layers of the glomerular capsule; the fluid filtered from the glomerular capillaries enters here.
What are the three layers of the filtrate membrane?
- fenestrated endothelia of glomerular capillaries
- basement membrane
- Podocyte-containing visceral layer of the glomerular capsule
how do the three of the filtrate membrane prevent passage of large proteins?
Has filtration slits to allow only water and solutes smaller than plasma protein
What is the role of glomerular mesangial cells?
If larger proteins get out to filtration slits, glomerular mesangial cells will degrade them
What are the parts of the renal tubule?
- A proximal convoluted tubule (PCT)
- Loop of Henle consists of a descending limb, a thin ascending limb, and a thick ascending limb.
- distal convoluted tubule (DCT)
What are some special histological features of the nephron?
• Single layer of epithelial cells forms walls of entire tube
• Distinctive features due to function of each region
– Podocytes
– Microvilli
– cuboidal versus simple
– Intercalated cells and principal cells
What is the role of the intercalated cells and principle cells and where are they found?
Found in the collecting duct and responsible for maintaining the acid-base balance of the blood
What is the juxtaglomerular apparatus (JGA)?
Structure where afferent arteriole makes contact with ascending limb of loop of Henle
What is the role of the juxtaglomerular cells and the macula densa cells?
Helps regulate blood pressure and the rate of blood filteration by the kidneys
How does nephron number change as you age?
Remains constant form birth – any increase in size of kidney is size increase of individual nephrons
How many of the nephrons have to work to have a functional kidney?
75%
What are the three main processes used to produce urine and where is each done in the nephron?
a) Glomerular filtration of plasma: glomerulus
b) Tubular reabsorption: from renal tubule to peritubular capillaries
c) Tubular secretion: from peritubular capillaries to renal tubule
What is glomerular filtration?
A passive process in which hydrostatic pressure forces fluids and solutes through a membrane.
What is the force that produces filtrate?
blood pressure
What are the three parts of the filtration membrane?
– a glomerular endothelial cell
– the basement membrane
– filtration slit formed by a podocyte
Is the glomerular blood pressure the only force involved in producing filtrate?
no
What are two opposing forces involved in producing filtrate?
- Capsular hydrostatic pressure (CP or HPc)
* Blood colloid osmotic pressure (COP or OPg)
What is the net filtration pressure?
About 10 mm hg
What is the glomerular filtration rate (GFR?)
• Amount of filtrate formed in all renal corpuscles of both kidneys / minute
Do small fluctuations in our arterial blood pressure affect GFR much?
no
What are the three mechanisms that regulate GFR?
- renal autoregulation,
- neural regulation,
- hormonal regulation.
What are the two ways the kidney regulates GFR by itself (autoregulation?)
- myogenic mechanism
* tubuloglomerular feedback mechanism
Which mechanism of renal GFR regulation involves the juxtaglomerular apparatus and the macula densa cells?
Tubuloglomerular feedback mechanism
What does activation of the sympathetic nervous system due to GFR?
- Rest: sympathetic activity is minimal; renal auto-regulation prevails
- Moderate activity: both afferent & efferent arterioles constrict equally; decreasing GFR equally
- Extreme activity (exercise or hemorage): vasoconstriction of afferent arterioles reduces GFR; lowers urine output & permits blood flow to other tissues
What are the two hormones that regulate GFR and when would each be activated (what are the effects of each on urine production / blood volume?)
• Angiotensin II reduces GFR
– potent vasoconstrictor that narrows both afferent & efferent arterioles reducing GFR
• Atrial natriuretic peptide (ANP) increases GFR
– stretching of the atria that occurs with an increase in blood volume causes hormonal release
• relaxes glomerular mesangial cells increasing capillary surface area and increasing GFR
What is tubular reabsorption?
Reclaiming of most of the tubule contents and returning it to blood
What are the two ways substances can be reabsorbed?
- Transcellular route
* Paracellular route
what is reabsorbed in the proximal convoluted tubule (PCT)?
- Water,
- organic nutrients,
- certain ions,
- lipid-soluble substances,
- CI-,
- K+, and
- urea.
What is reabsorbed in the DESCENDING limb of loop of Henle?
• Water
What is reabsorbed in the ASCENDING Limb of loop of Henle?
- Na+
- Cl2+
- K+
What is reabsorbed in the distant convoluted tubule (DCT)?
- Na+
- Cl-
- Ca2+
What hormones act on the DCT / collecting ducts?
Parathyroid hormone
What is the role of Antidieuretic hormone (ADH)?
- Increases water permeability of principal cells
* Stimulates the insertion of aquaporin- channels
What does ADH do to urine output?
Reduces it
What is tubular secretion?
Transfer of materials form blood into tubular fluid
What is secreted in collecting ducts?
- H+
* Excess K+
What is a countercurrent multiplier?
Create an increase in concentration in the loop
How does this multiplier form the medullary osmotic gradient?
- As the fluid is coming into loop, blood osmolarity is 300mOsm
- as move back up, levels will go back to low osmolarity.
What is a countercurrent exchanger?
The flow of blood through the ascending and descending portions of the vasa recta
How does the countercurrent exchanger preserve the osmolarity of the blood in the body?
It is highly permeable
How do the collecting ducts use the gradient set up by the loop to regulate urine osmolarity?
Due to the countercurrent multipliers (long nephron loops)and the countercurrent exchanger (vasa recta)
What are the two parts of the nephron / collecting ducts involved in forming concentrated urine?
- Ascending limb
* Medullary region
How is dilute urine formed?
• Water reabsorbed in thin limb, but ions reabsorbed in thick limb of loop of Henle create a filtrate more dilute than plasma
What are dieuretics?
Substances that slow renal reabsorption of water & cause diureses (increased urine flow rate)
How do caffeine and alcohol lead to increase urine production?
- Caffeine inhibits Na+ reabsorption
* Alcohol inhibits secretion of ADH
Where does urine go once it is collected in the collection ducts? How does it leave the body (eventually?)
- Urine (<-nephrons) drains through papillary ducts into minor calyces, which joint to become major calyces that unite to form the renal pelvis.
- From the renal pelvis, urine drains into the ureters and then into the urinary bladder, and finally, out of the body by way of the urethra
What is the trigone of the bladder?
smooth flat area bordered by 2 ureteral openings and one urethral opening
What kind of tissue lines the bladder and allows for its distension?
• Smooth muscle
What is a urethra?
Thin-walled muscular tube that drains urine form the bladder and out of the body
What is the micturition reflex? Is it voluntarily controlled ?
Urination (voiding), yes it’s voluntary
