(AnaPhy) Respiratory System — Lecture

Conduction Zone

• Nose

• Pharynx

• Larynx

• Trachea

• Bronchi

Respiratory Zone

Lungs — Aveoli

Upper respiratory tract

Includes passageways from the nose to larynx

Lower respiratory tract

Includes passageways from trachea to alveoli

Nostrils (nares)

Are the route through which air enters the nose

Conchae

Are projections from the lateral walls. Filters, moisten, and warms air

Meatus

Are air passages located in the lateral wall of the nasal cavity, beneath each of the three nasal conchae (also known as turbinates).

Paranasal Sinuses

Are cavities within the frontal, sphenoid, ethmoid, and maxillary bones surrounding the nasal cavity.

Oropharynx and laryngopharynx

• Serve as common passageway for air and food

• Epiglottis routes food into the posterior tube, the esophagus.

Pharyngotympanic tubes

open into the nasopharynx, and drains the middle ear

Pharyngeal tonsil (adenoid)

a single tonsil, is located in the nasopharynx.

Palatine tonsils

are located in the oropharynx at the end of the soft palate.

Lingual tonsils

are found at the base of the tongue.

Thyroid cartilage

Composition of the Adam’s apple

Larynx

• ‘Voice Box’

• Made of eight rigid hyaline cartilages

• Routes air and food into proper channels

• Plays a role in speech

Epiglottis

• Spoon-shaped flap of elastic cartilage

• Protects the superior opening of the larynx

• Routes food to the posteriorly situated esophagus and routes air toward the trachea

• During swallowing, rises and forms a lid over the opening of the larynx

Vestibular folds

The false vocal cords, are a pair of thick folds of mucous membrane located in the supraglottic larynx.

Vocal folds

• ‘True vocal cords’

• Vibrate with expelled air

• Allow us to speak

Trachea

• ‘Windpipe’

• Walls are reinforced with C-shaped rings of hyaline cartilage

• Lined with ciliated mucosa

Right Main Bronchus

This bronchus is shorter, wider, and more vertical. This anatomical difference makes it more likely for inhaled foreign objects to lodge there.

Left Main Bronchus

This bronchus is longer and narrower, It passes beneath the aortic arch and in front of the esophagus to reach the left lung.

Lobar (Secondary) Bronchi

Once inside the lungs, the main bronchi further subdivide.

Segmental (Tertiary) Bronchi

The lobar bronchi then branch out, each supplying a bronchopulmonary segment, which is a functionally independent unit of the lung tissue.

Pulmonary (visceral) pleura

lines the lung surface

Parietal pleura

lines the walls of the thoracic cavity, anchors / connect the lungs

Pleural fluid

• fills the area between layers

• Allows the lungs to glide over the thorax

• Decreases friction during breathing

Respiratory bronchioles

transitional airways in the respiratory system that connect the conducting airways to the gas-exchanging structures. They represent the beginning of the respiratory zone where gas exchange can occur.

Carina

A cartilaginous ridge located at the base of the trachea where it bifurcates (divides) into the two main bronchi.

Alveoli

Are tiny, balloon-shaped air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place. They are the functional units of the respiratory system.

pulmonary capillaries

Primary site of gas exchange: Oxygen diffuses from the alveoli into the blood, and carbon dioxide diffuses from the blood into the alveoli.

pulmonary veins

Transport oxygen-rich blood away from the lungs and back to the left atrium of the heart.

Alveolar macrophages (“dust cells”)

Add protection by picking up bacteria, carbon particles, and other debris. Are immune cells of the lungs

External respiration / Pulmonary gas exchange

• Oxygen is loaded into the blood

• Carbon dioxide is unloaded from the blood into the alveoli

Internal respiration / Tissue gas exchange

• Carbon dioxide is loaded into the blood

• Oxygen is unloaded from the blood into the tissue

Surfactant- secreting cell

• a lipid molecule

• Coats gas-exposed alveolar surfaces preventing collapse

• Secreted by cuboidal surfactant-secreting cells

Pulmonary ventilation

• Moving air into and out of the lungs (commonly called breathing)

• Mechanical process that depends on volume changes in the thoracic cavity.

Inspiration (Inhalation)

• Diaphragm and external intercostal muscles contract

• Intrapulmonary volume increases

• Gas pressure decreases

• Air flows into the lungs until intrapulmonary pressure equals atmospheric pressure

Expiration (exhalation)

• Largely a passive process that depends on natural lung elasticity

• Intrapulmonary volume decreases

• Gas pressure increases

• Gases passively flow out to equalize the pressure

• Forced expiration can occur mostly by contraction of internal intercostal muscles to depress the rib cage

External intercostal muscles

Are a group of eleven pairs of skeletal muscles located between the ribs. They are the most superficial layer of the three intercostal muscle layers

Intrapleural pressure

• the pressure within the pleural cavity, the potential space between the visceral pleura (covering the lungs) and the parietal pleura (lining the chest wall).

• Always negative

Tidal volume (TV)

• Normal quiet breathing

• 500 ml of air is moved in/out of lungs with each breath

Inspiratory reserve volume (IRV)

• Amount of air that can be taken in forcibly over the tidal volume

• Usually around 3,100 ml

Expiratory reserve volume (ERV)

• Amount of air that can be forcibly exhaled after a tidal expiration

• Approximately 1,200 m

Residual volume

• Air remaining in lung after expiration

• Cannot be voluntarily exhaled

• Allows gas exchange to go on continuously, even between breaths, and helps keep alveoli open (inflated)

• About 1,200 ml

Dead space volume

• Air that remains in conducting zone and never reaches alveoli

• About 150 ml

Functional volume

• Air that actually reaches the respiratory zone

• Usually about 350 ml

Nonrespiratory Air Movements

• Can be caused by reflexes or voluntary actions

• Ex: Coughing, sneezing, laughing, crying

Oxygen transport in the blood

• Most oxygen travels attached to hemoglobin and forms oxyhemoglobin (HbO2)

• A small dissolved amount is carried in the plasma

Carbon dioxide transport in the blood

• Most carbon dioxide is transported in the plasma as bicarbonate ion (HCO3 –)

• A small amount is carried inside red blood cells on hemoglobin, but at different binding sites from those of oxygen

Medulla

Sets basic rhythm of breathing and contains a pacemaker (self-exciting inspiratory center) called the ventral respiratory group (VRG)

Pons

modulating and regulating the activity of the medullary respiratory centers. It helps to ensure smooth and coordinated breathing patterns.