C3.2 - Mammalian Respiration

Respiration

• All mammals share the same basic respiratory structure
• Respiration subdivided into 3 activities
  1. Breathing: inspiration / inhalation (air in) [L] and exhalation / expiration (air out) [R]
  2. External Respiration: exchange of oxygen and carbon dioxide between air and blood
  3. Internal Respiration: exchange of oxygen and carbon dioxide between blood and cells of surrounding tissue

Respiratory Tract (RT)

• respiratory tract: the passageway of which air passes through the body
• Lungs protected deep within body
• Connected to exterior by passageways

Path of Oxygen in RT (Diagram)

flowchart TD
	air[**AIR**] --> a
	a[**Nose / Mouth**
	Filtered by nasal hair/mucus
	Warmed and moistened] --> b
	b[**Pharynx**
	Epiglottis blocks food to trachea] --> c
	c[**Larynx**
	Vocal cords in here vibrate to make sounds] --> d
	d[**Trachea**
	Held up by cartilageous rings] --> e
	e[**Bronchi**] -- ***To Lungs*** --> f
	f[**Bronchioles**] --> g[**Alveoli**]

The Upper RT

• Air enters nostrils (nares) or mouth
• Air is warmed and moistened by hair and mucus in nose
• Air passes through pharynx, glottis, and larynx
• pharynx: junction of esophagus, trachea, nasal cavity, and larynx
• esophagus: passageway to stomach
• glottis: opening of trachea
• trachea (windpipe): flexible passageway to lungs, supported by cartilaginous rings
• epiglottis: flap preventing food and liquids passing into the trachea
• larynx: voice box housing vocal chords
• cilia: microscopic hairs in the body
• Upper RT line w/ cilia that continually pass foreign particles, fluids, and debris up and out of RT

The Lower RT

• Trachea branches into 2 bronchi, one for each lung
• Lungs divided into lobes:
  • 3 on right
  • 2 on left
• Bronchi then branch into many bronchioles
• Bronchioles end in grape-like clusters of alveoli

RT Lining

• Lined with moist epithelial tissue (from 4 types of tissue)
• Epithelial tissue covered with cilia and fine layer of mucus in trachea and bronchi
• Mucus traps foreign particles and removes them from air
• Cilia sweep mucus-trapped particles up to pharynx for disposal or swallowing

Alveoli

• alveoli: sacs in lungs where gas exchange takes place
• One cell thick
• Closely associated w/ capillary networks
• Blood takes up oxygen through simple and facilitated diffusion
• Alveoli coated in surfactant to reduce surface tension

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• Inner surface of each alveolus lined with layer of moist epithelial cells
• Oxygen in air dissolves in film of moisture on these epithelial cells
• Oxygen diffuses into capillaries and binds to hemoglobin on RBCs
• Hemoglobin increases efficiency by creating diffusion gradient
• RBCs transport oxygen throughout the body