A&P II- Respiratory I

Respiratory System

Structurally, upper and lower divisions or tracts.

• upper respiratory tract nose, pharynx, larynx

• lower respiratory tract larynx, trachea, bronchi and lungs

Functionally, conducting zone and the respiratory zone.

• conducting zone: brings air to/from the site of gas exchange (external respiration): nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles.

• respiratory zone : main site of gas exchange : respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli

Air passing through the respiratory tract traverses the:

• Nasal cavity

• Pharynx

• Larynx

• Trachea

• Primary (1o) bronchi

• Secondary (2o) bronchi

• Tertiary (3o) bronchi

• Bronchioles

• Alveoli (150 million/lung)

Respiratory structures

• External nose is visible on the face.

• Internal nose: cavity beyond the nasal vestibule. divided by nasal septum.

Function:

• Filter, warm, moisten incoming air

• Smell incoming air

• Resonating chamber

Three nasal conchae (or turbinates): protrude from each lateral wall.

• Meatus under each nasal concha, for a duct that drains secretions of the sinuses and tears into the nose.

• Increases turbulence mixing air for moisture and warmth

Pharynx: hollow tube starting posterior to the nasal cavity and descending to the opening of the larynx in the neck.

It functions as:

• a passageway for air and food

• a resonating chamber

• a housing for the tonsils

3 anatomical regions:

• The nasopharynx; oropharynx; and laryngopharynx

Upper Respiratory Tract

Most of the Respiratory tract is lined with ciliated pseudostratified columnar tissue

• Cilia move mucous and trapped particles toward the pharynx and into the digestive tract

• Larynx: composed of 9 pieces of cartilage: connects the laryngopharynx with the trachea (the “windpipe”). prevents food and water from entering the lower respiratory system

• Resonating chamber

Epiglottis: flap of elastic cartilage covered with a mucus membrane, attached to the root of the tongue.

• guards the entrance of the glottis, the opening between the vocal folds.

• As air passes from the laryngopharynx into the larynx, it leaves the upper respiratory tract and enters the lower respiratory tract.

Lower Respiratory Tract

Trachea

• semi-rigid pipe of semi-circular cartilaginous rings, anterior to the esophagus. extends from the larynx into the mediastinum where it divides into right and left primary (1o, “mainstem”) bronchi.

It is composed of 4 layers:

• a mucous secreting epithelium: mucosa

• three layers of CT (submucosa, hyaline cartilage, and adventitia)

Tracheal cartilage rings are incomplete posteriorly, facing the esophagus.

• Esophageal masses can press into this soft part of the trachea and make it difficult to breath, or even totally obstruct the airway

Primary (1o or “mainstem”) bronchi

• emerge from the inferior trachea at the carina

• go to the lungs, situated in the right and left pleural cavities

1o bronchi divide to form 2o (supply lobes) and 3o bronchi (supply segments) of each lung.

• 3o bronchi divide into bronchioles

  • branch through about 22 more divisions

  • The smallest are the terminal bronchioles.

As bronchi and bronchioles branch and become smaller.

• mucous membrane changes from columnar to cuboidal

• cartilaginous rings become more sparse, and eventually disappear altogether.

• Smooth muscle increases.

  • Sympathetic stimulation: airway dilation

  • Parasympathetic stimulation: airway constriction

Lower Respiratory Tract 2

• Trachea to the terminal bronchioles: conducting airways – they do not participate in gas exchange

Alveoli participate in gas exchange

• Connected to respiratory bronchioles (simple cuboidal epithelium) and alveolar ducts (Simple squamous)

Pulmonary lobule.: alveoli, alveolar sacs, respiratory bronchioles, alveolar ducts and a terminal bronchiole

• the functional unit of the lung

• wrapped in elastic C.T.

Alveoli: composed chiefly of type I alveolar cells, allowing for exchange of gases with pulmonary capillaries.

• Type II cells: secrete surfactant that prevents collapse of the alveoli during exhalation.

Alveoli macrophages remove microscopic debris

The Lungs

The lungs receive blood via two sets of arteries

• Pulmonary arteries carry deoxygenated blood from the right heart to the lungs for oxygenation

• Bronchial arteries branch from the aorta and deliver oxygenated blood to the lungs (primarily the muscular walls of the bronchi and bronchioles)

• Ventilation-perfusion coupling: matches perfusion (blood flow) of areas in the lungs to ventilation (airflow) in that area

Lungs are divided into lobes by fissures.

• The right lung: oblique and horizontal fissure: 3 lobes

• The left lung: oblique fissure: 2 lobes

• Each lobe receives it own 2o bronchus that branches into 3o segmental bronchi (which continue to further divide)

• Apex of the lung: superior, extends slightly above the clavicles.

• Base of the lungs: on the diaphragm.

• Cardiac notch – (indentation for the heart) makes the left lung slightly smaller than the right lung.

Each lung is enclosed by a double-layered pleural membrane.

• parietal pleura: line the walls of the thoracic cavity.

• visceral pleura: adhere tightly to the lungs

On each side of the thorax, a pleural cavity is formed.

• The integrity is crucial to the mechanism of breathing.

• Pleural fluid: reduces friction.

• Mechanical coupling: surface tension moves two layers together