Mechanics of Breathing and Respiration

• Mechanics of breathing involves exchanging gases, regulating pH, protecting against pathogens, vocalizing, and secreting hormones like ACE
• Bulk flow goes from high to low pressure, generated by a muscular pump (diaphragm)
• Airflow resistance depends on the diameter of the tubes

Respiration Types

• External respiration exchanges O2 and CO2 between lungs and blood and transports O2 & CO2
• Internal respiration exchanges gases between blood and cells
• Pulmonary circulation's capillaries facilitate diffusion (simple squamous)
• Ventilation moves gases in and out
• Gas exchange goes from tissue to circulatory system
• Cellular respiration generates ATP

Pleural Sacs

• Pleural sacs (visceral and parietal) enclose lungs within the thoracic and pleural cavities
• Serous fluid reduces friction and holds lungs against the thoracic wall
• Pleuritis is inflammation of the pleura and causes respiratory issues

Respiratory System Components

• The upper system includes the pharynx (non-keratinized stratified squamous), epiglottis (elastic cartilage), vocal cords, and nasal cavity
  • Pharyngitis is an example
• The nasal cavity regulates temperature, humidification, and filtration
• Nasal plasticity is adaptation to mouth breathing
• The lower system includes the trachea (hyaline cartilage/no fibers + pseudostratified ciliated columnar), right/left lungs and bronchus (pseudostratified ciliated columnar), and bronchioles (pseudostratified ciliated columnar)
• The diaphragm facilitates respiration
• Goblet cells/mucosal secrete mucus (mucin is a glycoprotein)
• Fissures separate lobes

Alveoli

• They are the primary site of gas exchange (simple squamous)
• Type 1 cells make up alveolar air sacs which facilitate gas exchange
• Type 2 cells release surfactant to decrease surface tension
• Type 3 cells are macrophages (immune cells)
• Blood flow: Right ventricle → Pulmonary Trunk → Pulmonary Arteries → Lung → Pulmonary Vein → Left Atrium

Bronchi Types

• Primary
• Secondary
• Tertiary
• From trachea to bronchioles, hyaline cartilage is lost increasing permeability and diffusing capacity

Gas Laws

• Atmospheric pressure is 760 mmHg (1 ATM); higher is below sea level
• Dalton’s law outlines that total atmospheric pressure equals the sum of all partial pressures
• Nitrogen has the highest atmospheric concentration
• Boyle’s law describes that pressure is inversely proportional to volume: P=1/V
  • Increased volume = decreased pressure
  • Decreased volume = increased pressure

Lung Volumes

• Tidal volume (VT) is the air volume during one quiet breath
• Inspiratory reserve volume (IRV) is the additional volume above tidal volume during forced breathing
• Expiratory reserve volume (ERV) is the volume forcefully exhaled after normal expiration during forced breathing
• Residual volume (RV) is the remaining air volume after maximal exhalation

Lung Capacities

• Vital capacity (VC) = IRV + ERV + tidal volume
• Total lung capacity (TLC) = Tidal volume + IRV + ERV + residual volume
• Inspiratory capacity = TV + IRV
• Functional residual capacity = ERV + RV

Diaphragm Functions

• The Phrenic nerve regulates the diaphragm, inflamed leads to hiccups
• During inspiration, gas enters as thoracic volume increases with diaphragm contraction/flattens
• During expiration, the diaphragm relaxes, and volume decreases while pressure increases

Intrapleural Pressure

• It is usually negative
• Pneumothorax occurs if gas enters, causing collapse One-way valve is treatment
• Hemothorax is blood in the lung, causing collapse
• Inspiration drops pressure
• Expiration restores normal pressure

Ventilation Types

• Hyperpnea is rapid breathing due to metabolic demand and exercise
• Hyperventilation is rapid breathing unrelated to metabolic demand, emotional
• Hypoventilation is shallow breathing and asthma
• Tachypnea is fast breathing, panting
• Dyspnea is difficult breathing and pathologies
• Apnea is complete cessation of breathing, sleep apnea

Lung Diseases

• Obstructive diseases involve difficulty expiring due to increased compliance/low elastins
  • Sleep apnea, COPD, epidema, chronic bronchitis are all obstructive
• Respiratory acidosis is compensated metabolically through increased bicarbonate reabsorption
• Restrictive diseases involve difficulty inspiring due to increased elastin/low compliance
• Respiratory acidosis is also a factor
• Forced Vital Capacity differentiates lung physiology

Gas Exchange

• Occurs in alveoli, capillaries, and tissues
• Regulated variables include O2, CO2, and pH

Hypoxia and Hypercapnia

• Hypoxia is low O2 and high CO2
• Hypercapnia is a buildup of CO2, acidic
• Passive transport follows concentration gradients
• High to Low Concentration

Alveoli/Blood

• PO2 in alveolar air is greater than PO2 in blood
• PCO2 in blood is greater than PCO2 in alveolar air

Blood/Tissues

• Oxygen in blood is higher than in tissue: PO2 blood > PO2 tissue
• PCO2 tissue > PCO2 blood
• Deoxygenated Blood: 40 mm Hg
• Oxygenated Blood: 100 mm Hg

Ventilation Pressures

• During expiration, P(in) > P(out)
  • Decreased Diaphragm, V and P
• During inspiration, P(out) > P(in)
  • Increased Diaphragm, V and decreased P
• Low Alveolar PO2 decreases O2 uptake

Inspired Air

• Alveolar ventilation becomes inadequate and low O2
• Hypoventilation causes abnormal oxygen
• Higher altitude decreases PO2
• Decreased lung compliance (asbestosis)
• Increased airway resistance (COPD)
• CNS depression occurs from alcohol poisoning or drug overdose and affects respiratory center in the brainstem
• High Compliance = difficulty with expiration (build up of CO2)
• High Elastins = difficulty with inspiration (pulmonary fibrosis)

Gas Exchange in Alveoli

• Cells form a diffusion barrier between lung and blood
• O2 moves from alveoli to plasma, binding to hemoglobin
• CO2 diffuses from plasma to alveoli

Hypoxia Causes

• Body doesn’t receive enough oxygen if you have hypoxia
• Emphysema: Destroys alveoli reducing surface area for gas exchange, less oxygen absorbed into bloodstream
• Fibrotic Lung Disease: thickens alveolar membrane, slows gas diffusion, losing lung compliance
• Pulmonary Edema: Accumulates fluid in interstitial spaces, increasing diffusion distances
• Asthma: Increases airway resistance due to bronchoconstriction; needs adrenergic receptors

Gas Transport

• Oxygen dissolves in plasma, then binds to hemoglobin
• Hb + O2 ↔ HbO2 (oxyhemoglobin- reversible reaction allowing O2 to be released when needed)
• 4 hemes = 4 O2 binding-sites Gas Transport in Blood
• ↑PO2 shifts reaction to R in lungs
• ↓PO2 shifts reaction to L in tissues
• Ensures RBCs become saturated with O2 before traveling through bloodstream

Carbon Dioxide Transport

• Formate ion (HCO3) maintains acid-base balance & ensures removal of metabolic waste
• Diffusion occurs
• Binds to hemoglobin to make carboxyhemoglobin
• Is transported in bloodstream, reacts w/ water and RBC = carbonic acid
• Chloride movement maintains homeostasis and pH levels
• bicarbonate
• Bicarbonate= non-metal to non-metal (covalent bond)

Medulla Neurons

• Visceral sensory command is ex. BP (baroreceptors found in aortic arch/carotid arteries)
• Medulla Oblongata (primary regulator) & Pons – activates Phrenic Nerve
• Dorsal respiratory group (DRG) receives input from VRG
• Diaphragm receives signals from Phrenic nerve via pons & medulla
• Rate is modulated by central/peripheral chemoreceptors for CO2, O2, and pH

Respiration

• Pontine group refines breathing patterns
• Ventral group manages forced respiration
  • Contains the pre-Bötzinger complex which controls breathing

Ventilation Factors

• Ventilation is influenced by CO2, O2, & pH
• Peripheral chemoreceptors in carotid bodies sense PO2, pH, and PCO2 changes
• Low PO2, pH + high PCO2 = increased ventilation
• O2 must fall below 60 mm Hg to trigger reflex
• Central chemoreceptors in CNS respond to PCO2 changes in CSF

Digestive System Anatomy

• Gastrointestinal system/ Alimentary Canal has 2 components
• Oral cavity begins digestion in mouth and pharynx
• Gastrointestinal tract(GI Tract)

Digestive Functions

• Food travels through the digestive system
• Digestion (mechanical and chemical) occurs through the system
• Sphincters divide the tract
• Accessory organs secrete digestive material
• Chyme is essential for nutrient breakdown
• Food goes through tract by way of processes
• Waste is excreted from the GI tract by way of the anus
• Digestive system is exposed to an external environment
  • GI is home to commensal microorganisms

Salivary Glands

• Salivary Secretion is autonomic control (involuntary)
• Contain digestive enzymes (amylase) to prepare food
• 3 Types of glands (glossopharyngeal nerve):
  • Parotid contains watery solution of enzymes(amylase)
  • Submandibular contains a mixed water and saliva
  • Sublingual contains mucus with saliva

Segments of Digestion

• Esophagus- peristalsis; coordinated contractions assist food movement
• Stomach- the fundus for immunity, storage, and digestion.
• Pylorus-controlled by pyloric valve

Small Intestine

• Nutrients are absorbed in this area
• Contains villi and crypts

Large Intestine

• Large intestine is where water and nutrients are reabsorbed.
• Feces Expels food/ waste
• Colon and Rectum with an external anal sphincter
• The GI Tract wall has 4 layers
• Mucosa
  • consists of specialized epithelium
  • includes a lamina propria(connective tissue)
  • consists of muscularis mucosae
• Submucosa helps structural support
• Muscularis Externa has circular and longitudinal
• Serosa helps create protection

Processes

• Has basic processes beginning with Digestion
• Digestion involves mechanical and chemical means
• Absorption and GI Lumen, and ECF(nutrients; carbohydrates, fats, vitamins)
• Secretion assists release
• GI- motility is another aid

###Motility

• Assists mechanical mixing and regulation of food passage
• Tonic and Phasic Contractions occur.
• Electrical impuleses regulate motility
• Migrating motor complex assists process
• contractions
• Peristalsis Peristalsis – contraction over contraction (esophagus) and segmental contraption

###Regulation of the GI

• The GI tract consists contains short reflex as assisted by enteric nervous system and parasympathetic nervous system
• The digestive system contains growth, and an internal and external maintenance of certain information, like diffusion and integration
• Contains a long reflex, where a Cephalic occurs

###Cehpalic

• Anticipation & stimulation act as key points where a cephalic phase begins prime the GI tact. Has anticipatory response
• Reflex secretions begin
• Functions with chemical actions
• Contains taste and certain digestion actions
• Stimulations: Inhibits somatostatin to allow acid production; parietal cells secrete HCl and pepsinogen

###Deglutition

• The swallowing effect
• Is a phase that is controlled by one's medulla. Muscle activates pushing food (swallowing)

###Gastirc Phase The digestion cycle and enzyme action begins with:

1. immunity
2. storage
3. digestion
4. defense

• Histamine assists acid Function cycle follows with: Promotes histamine to stimulate acid secretion and positive feedback

###Secretion Function Consists of:

• gastrin/secretin production
• parietal cells which are the key to acid secretion
• mucosa actions
• Enzyme and paracrine
• Chief cells create pepsinogen to pepsin (active) & gastric lipase
• Intrinsic factor secreted to absorb Vit. B-12 & bring into bloodstream to marrow for RBC formation helps help prevent auto-digestion
• prevents Mucosal Cell and internal phases
• Motility Control
• Mainly intestinal as it contains villi