2 Mammalian Respiratory System Mammals (yes that includes humans – Gifty) have a very complex respiratory system that includes:Breathing = taking air into the lungs (inspiration), and forcing air out of the lungs (expiration)External respiration = the exchange of O2 and CO2 between air and bloodInternal respiration = the exchange of O2 and CO2 between blood and the cells of the surrounding tissueCellular respiration = the complex series of chemical reactions in the mitochondria of cells that uses O2 to produce ATP and CO2
3 The Respiratory TractMammalian lungs must be shielded within the body:To prevent water loss – the respiratory surface must be moistTo guard against damage – lungs are delicate, fragile structures with many folds and fine membranesProtected deep within the body by the bone and muscular structure of the thoracic cavity.Therefore, we need a passageway to allow air to move from the external environment to the respiratory surface deep inside the body
6 The Upper Respiratory Tract Air first enters through the nostril cavityOr in humans and many other animals, also through the mouthAir passes through hollow nasal passages which contain thin bones, called turbinates, that hang suspended from the nasal chambersIncreases the surface area of the nasal chambers and secrete mucus to moistens the incoming airThe cell linings of the nasal chambers and the turbinate bones are well supplied with capillarieswarm the incoming airincrease its relative humidityServes to protect the delicate lung tissue
9 Upper Respiratory Tract Air then passes through the pharynx, the glottis, and the larynx:The pharynx connects the mouth and nasal cavity to the larynx and esophagusThe glottis is the opening of the trachea, the passageway that conducts air to the lungs.This opening is protected by the epiglottisThe pharynx is the dividing point between the trachea (air) and the esophagus (food)
11 Upper Respiratory Tract The larynx, or “voice box,” contains the two folded structures of the vocal cords.When you breathe normally, there is a large gap between the two cords.When you prepare to speak, muscles around the larynx contract, bringing the cords closer together.The passage of air through this narrower space causes the cords to vibrate, producing a sound.The pitch of the sound varies with the length of the cords:a long cord produces a low sounda shorter cord produces a higher sound.At puberty, the vocal cords of males grow quickly
14 Upper Respiratory Tract After the larynx, air goes down the flexible tube of the trachea.The trachea is supported in part by semicircular cartilage rings.Prevent the trachea from collapsingThe nasal and other passages of the upper respiratory tract are lined with ciliated cells that secrete mucus.Traps foreign particles such as dust and bacteriaThe cilia helps to propel this material back into the nose and throat where it can be expelled by coughing or sneezing.So why do we cough/sneeze more when we’re sick?
16 The Lower Respiratory Tract The trachea branches into two smaller passageways called bronchi (singular bronchus)One bronchus enters each lungEach bronchus subdivides many times to produce a network of finer and finer tubes called bronchioles.the bronchi and bronchioles are also lined with a ciliated mucous membrane.
18 Lower Respiratory Tract Each bronchiole ends in a grape-like cluster of tiny sacs called alveoli (singular alveolus).In the moist alveoli is where the actual exchange of gases takes placeThe wall of each alveoli is one cell thick and is adjacent to a network of tiny capillariesThese capillaries are the site for the exchange of oxygen and carbon dioxide in the body.Most of the exchange of gases takes place through simple diffusion, but facilitated diffusion accounts for some (possibly as much as 30%)This allows the blood to take up oxygen more quickly than would otherwise be possible.
20 Lower Respiratory Tract In the spaces between the individual structures of the respiratory tract is elastic connective tissueKeeps the alveoli and bronchi in a relatively permanent positionThe alveoli are also lined with a lubricating film that helps to keep them from collapsing
21 Lower Respiratory Tract Each lung is divided into lobes.The right lung has 3 lobesThe left lung has only 2. Why?To accommodate the heartThe lungs themselves are enveloped in layers of tissue called pleura.A flexible membrane that contains the lungs while still allowing them to expand and contract during inspiration and expirationEach pleuron is made up of two layers separated by a thin film of lubricating fluid