Respiratory System Flashcards
Types of Respiration
External: Gaseous exchange between air and blood (lungs)
Internal: Gaseous exchange between blood and tissues (tissues)
Nose
- Inspired air through nostrils (external nares) leading into the nasal cavity (divided by cartilaginous septum ~ R+L nasal chambers)
- Hairless pad of epidermis, thick layer of stratified squamous epithelium>mucous and sweat gland: rhinarium
- Bone in chambers (turbinates/conchae) covered in ciliated mucous epithelium ~ blood capillaries
- Alar fold = small bulbous dwelling visible through nostril
- Back of nasal chambers, mucous epithelium (rich supply of sensory nerve endings) respond to smell (olfactory region)
- Nerve fibres = cribriform plate (ethmoid bone) olfactory bulbs of forebrain ~ remainder of mucous membranes is the respiratory region
- Turbinates and ciliated mucous epithelium ~ warm and moisten incoming air. Cilia and mucous trap particles, waft to back of nasal cavity, pharynx then swallowed.
Paranasal sinuses:
- sinus = air-filled cavity within a bone
- lie within facial bones of skull
- lined with ciliated mucous epithelium
~ lighten weight of skull, heat exchange, mucus secretion
Pharynx
- Nasal cavity > pharynx
- Region at the back of the mouth shared by the respiratory and digestive systems
- Dorsal nasopharynx + ventral oropharynx
- Musculomembranous partition (soft palate) divides the two
- Soft palate extends caudally from hard palate ~ prevents food entering nasal chambers
- Oropharynx ~ food > oral cavity > oesophagus
- Nasopharynx ~ air > nasal cavity > larynx
Larynx
- Caudal to pharynx
- Regulate flow of gases
- Prevent other gases entering
- Suspended from skull by hyoid apparatus: hollow, box-like, number of cartilages (muscle + connective tissue)
- Rostral = epiglottis (elastic cartilage) > seal larynx entrance
- Larynx ~ resting, epiglottis = open
- Pair of vocal ligaments
- Mucous membrane covering = vocal folds
- Air moves past = vocal folds vibrate = sound
Trachea
- Larynx > Trachea
- Permanently open tube ~ attached to caudal border of laryngeal cartilages
- Ventral aspect of neck (below oesophagus)
- Pass through cranial thoracic inlet ~ enters mediastinum + terminates at a bifurcation (above the heart)
- Lumen ~ kept open (C-shaped rings of hyaline cartilage) ~ prevents collapse when thoracic pressure drops
- Flexible ~ allow movement of head and neck
- Cartilage rings connected by fibrous tissue + smooth muscle fibres
- Ciliated mucous epithelium > mucous traps particles, cilia “sweep” mucous to pharynx (spit out or swallow)
- Coughing reflex ~ aims to expel foreign particles
Bronchi/Bronchioles
- Trachea divides into left and right bronchi ~ each enters lung
- Bronchi branch to bronchioles
- Bronchi supported by rings of cartilage but this decreases down the bronchi > bronchioles
- Bronchioles branch into alveoli (via alveolar ducts)
- Walls contain smooth muscle (controlled by autonomic nervous system)
Alveoli
- Alveolar ducts ends at alveolar sacs
- Alveolar sacs = large numbers of alveoli (small, thin-walled sacs surrounded by a network of capillaries)
- Epithelial lining (pulmonary membrane) ~ thin for gas exchange
- O2 moves in, CO2 moves out
- Large numbers = large SA
Lungs
- Within thoracic cavity
- Either side of mediastinum
- Air passages, blood vessels and connective tissue surrounded by pulmonary pleura
- Left lung ~ 3 lobes
- Right lung ~ 4 lobes (4th is accessory)
- Cranial/Apical, Middle/Cardiac + Caudal/Diaphragmatic
Thoracic Cavity
- Right + Left pleural cavities
- Mediastinum
- Lined with serous membrane
- Secretea serous ~ reduce friction (lungs move)
- Diaphragmatic (cranial aspect of diaphragm)
- Pulmonary (R + L lungs)
- Costal (Inner side of ribs)
- Mediastinal (mediastinum)
Mechanics of Respiration
Diaphragm:
Dome-shaped muscular structure>boundary between thoracic and abdominal cavities>supplies nerves by phrenic nerve>contracts (flattens, increases volume)>relax (rises, decreases volume)
External Intercostals:
Fill intercostal spaces>supplies nerves by intercostal nerves>contract (ribs up+out, increase volume)>relax (ribs down+in, decrease volume)
Internal Intercostals:
Fill intercostal spaces>deep in the external intercostal muscles>supplies nerves by the intercostal nerves>passive except in forced expiration (contract alongside abdominal muscles)
Controlling Respiration
- Pons and medulla of hindbrain > respiratory centres (inspiration/expiration)
- Pneumotaxic + apneustic centres (expiration)
- Inspiratory centre (inspiration) ~ inhibited > apneustic centre > expiration > Hering-Breuer reflex = prevents overinflation of the lungs
- Stretch Receptors*>walls of bronchi/bronchioles>monitor degree of stretching
- Chemoreceptors*>peripheral (aortic + carotid bodies)>central (medulla of brain) ~ sensing CO2 levels>monitor O2 levels + pH of blood
Definition
Tidal Volume: Air passing into and out of the lungs in each respiration
Inspiratory Reserve Volume: Air inhaled during forced inspiration
Expiratory Reserve Volume: Air forcibly exhaled during expiration
Residual Volume: Air left in the lungs during expiration
Vital Capacity: Total amount of air that can be expired
Total Lung Capacity: RV, ERV, TV, IRV
