Organs of the Respiratory System

• Nose

• Pharynx

• Larynx

• Trachea

• Bronchi

• Lungs

Accessory Structures

• Thorax

• Diaphragm

The Nose

The nose (naso or rhino) acts as entrance for air and exit for carbon dioxide. A

ciliated epithilial mucus membrane lines the nose and much of the respiratory tract. It serves as a filter for dust and other foreign material. It warms and

moistens entering air and has olfactory receptors

The nostrils (nares) are paired openings. The nostrils vary in

pliability and expandability. The horse has pliable and expandable nostrils because mouth breathing

is not characteristic. The expandability accommodates the

increased need for oxygen

The PharynxThis is a musculomembranous saclike structure. The upper

portion is attached to the base of the skull and the lower portion unites with the esophagus. The pharynx unites with the nasal chambers, mouth, larynx and

eustasian tubes.

The pharynx is divided into three parts:

*nasopharynx*oropharynx

*laryngopharynx

The pharynx is used as passage for both air and food. Depending on the species it may also have a

roll in vocalization

The LarynxThis is commonly called the voice box and is located just below the

pharynx and it serves as a passage for air. The epiglottis is a lid like structure that prevents food from

entering the airway during swallowing

The larynx plays an important role is creating sound. Air passes

through the glottis during expiration causing a vibration,

producing a sound. (video)

The Tracheaalso called the windpipe is a

tube formed of smooth muscle with numerous C shaped rings of cartilage embedded in the tissue. These rings prevent collapse of the structure.

The Bronchithe ends of the trachea separates into smaller airways called the primary

bronchi

The bronchi is lined with a ciliated mucous membrane and have C shaped cartilage rings.

These rings become complete as the bronchi enter the lungs. They then divide into smaller branches

called the secondary branches and these divide into bronchioles which further divide into aveolar

ducts

The aveolar ducts terminate into the aveolar sacs which are

minute, squamous epithelium lined spaces that allow the lungs to achieve the primary function of oxygen and carbon dioxide

exchange.

As the bronchioles get smaller, the cartilage rings begin to

disappear. There are no rings in the aveolar ducts, sacs or aveoli.

The lungs are the primary structures of the respiratory system. The lungs occupy

almost the entire thoracic space. Each lung contains millions of

aveoli and capillaries.

The lungs are encased in a serous membrane called the visceral pleura. The thoracic cavity is lined with another membrane

called the parietal pleura. These membranes reduce the friction

during repiration

The space between these membranes is called the pleural

cavity or potential space.

The thorax (chest cavity) is lined with a membrane similar to the

covering of the lungs. This allows the lubrication of both

surfaces during respiration This membrane is divided into the:

*right pleural cavity*left pleural cavity

*mediastinum

The mediastinum contains the heart, thymus, esophagus,

trachea, bronchi, nerves, arteries, veins and lymphatic vessels.

The Diaphragm:This is a dome shaped

musculomembranous partition separating the thoracic and

abdominal cavity. It attaches to the lumbar and abdominal

cavities. It attaches to the lumbar vertebra, lower ribs and sternum

The diaphragm is the primary muscle of respiration. During

inspiration, it contracts, flattens and lowers. This increases the capacity of the thoracic cavity.

On expiration the diaphragm relaxes and returns to it’s normal

position

Video part 2 and 3

WARNING!!!!

This video of the anatomy of humans….it is graphic.

The process of respiration:The respiratory cycle is divided

into three parts:*inspiration*expiration

*rest : the interval between inspiration and expiration

Respiration involves oxygen being passed throughout the body by circulation and carbon dioxide

wastes being exhaled. The amount of oxygen retained by tissue depends on the need.

Tissue does not store oxygen and tissue only takes in as much

oxygen as it needs.

During exercise the oxygen requirement can be more than

doubled. The flow of air in and out of the lungs depends on

changes in the thoracic cavity. Inspiration and expiration are in

accordance with the pressure differences between the

atmosphere and air in the lungs

Tidal volume (TV):the volume of air inspired or

expired during ordinary respiration

Inspiratory reserve volume (IRV):

the maximum volume of air that can be forcibly inspired in

addition to tidal air.

Expiratory reserve volume (ERV):

the volume of air that can be forcibly expelled in addition to tidal air. Some air will always

be trapped in the alveoli no matter how forcibly an animal

exhales due to intrathoracic pressure.

Residual Volume (RV):The volume of air trapped in the

alveoli

Minimal volume:the small amount of air left in the alveoli after a total lung collapse.

When the thoracic pressure is equal to the atmospheric pressure

Vital capacity (VC):the largest amount of air that can be moved in and out of the lungs.

The sum of the total of inspiratory and expiratory

reserve volumes plus the tidal volume

The nerves from the brain that pass down the chest wall and

diaphragm to control respiration

Vagus nerve:originates in the brain and sends

branches to the larynx, heart, bronchi, esophagus, stomach, liver

and abdomen.

Phrenic nerve:originates in the cervical spine and passes to the diaphragm

Thoracic nerve:originates in the thoracic spinal cord, these are the nerves of the

muscles of the thorax