Respiratory System Overview

Respiratory System Overview

• All organs constantly use oxygen (O2) and release carbon dioxide (CO2).
• Gas exchange increases when organs are active.
• The respiratory system delivers atmospheric oxygen to the blood for distribution throughout the body, and removes carbon dioxide.

Respiratory System Organs

• Nose
• Pharynx
• Larynx
• Trachea
• Bronchi
• Bronchioles
• Lungs
• Pleura (covering the lungs)
• Muscles of breathing (intercostal muscles and diaphragm)

Nose and Nasal Cavity

• The nasal cavity is the primary air entry point.
• It's a large, irregular cavity divided into two passages by a septum.
• The posterior septum is bony (perpendicular plate of the ethmoid bone and vomer).
• The anterior septum is made of hyaline cartilage.
• The roof includes the cribriform plate of the ethmoid bone, as well as the sphenoid, frontal, and nasal bones.
• The floor is formed by the hard palate (maxilla and palatine bones) and soft palate (muscles).

Lining of the Nasal Cavity

• Ciliated columnar epithelium lines the nasal cavity.
• It has mucus-producing goblet cells.
• The epithelium blends with the skin at the nostrils and extends posteriorly into the nasopharynx.

Openings into the Nasal Cavity

• Anterior nares (nostrils): external openings to the nasal cavity.
• Posterior nares: openings from the nasal cavity to the pharynx.
• Paranasal sinuses: air-filled cavities in facial and cranial bones.
• Important sinuses include maxillary, frontal, sphenoid, and ethmoidal sinuses.
• Sinuses aid speech and lighten the skull; the nasolacrimal ducts drain tears from the eyes into the nose.

Functions of the Nose

• Warms, moistens, and filters inhaled air.
• The three conchae (scroll-shaped structures) increase surface area and create turbulence.
• This promotes better mixing of inspired air with the nasal mucosa, facilitating warming, humidification, and filtration.
• Olfaction (smell) occurs due to specialized receptors in the roof of the nose and superior conchae.

Pharynx (Throat)

• The pharynx is a 12-14 cm passageway behind the nasal cavity, mouth, and larynx, leading to the esophagus.
• It's divided into three regions: nasopharynx, oropharynx, and laryngopharynx.
• Nasopharynx: superior; communicates with nasal cavities.
• Oropharynx: middle; connects to oral cavity and laryngopharynx.
• Laryngopharynx: inferior; connects to the larynx and narrows into the esophagus.

Nasopharynx

• Lies behind the nose above the soft palate.
• Contains openings for auditory tubes.
• The pharynx contains pharyngeal tonsils (adenoids) on its posterior wall.

Oropharynx

• Lies behind the mouth, from the soft palate to the upper part of the third cervical vertebra.
• Lateral walls blend with the soft palate to form folds.
• Palatine tonsils are located between the folds.
• Prevents food or fluids from entering the nasal cavity during swallowing.

Laryngopharynx

• Connects oropharynx to esophagus and larynx.
• Air and food pass through.

Larynx (Voice Box)

• Connects the laryngopharynx and trachea.
• Located in front of the 3rd-6th cervical vertebrae.
• Composed of cartilage, ligaments, and muscles.
• Important components include hyoid bone, thyroid cartilage, cricoid cartilage, arytenoid cartilages, and epiglottis.

Larynx Structure (Cartilages)

• Thyroid cartilage (largest): forms anterior and lateral walls (Adam's apple).
• Cricoid cartilage (ring-shaped): located below the thyroid cartilage.
• Arytenoid cartilages (paired): top of the cricoid cartilage, responsible for vocal cord movement.
• Epiglottis (leaf-shaped): covers the larynx during swallowing.

Larynx Structure (Interior)

• The vocal cords are folds of mucous membranes, extending between the thyroid and arytenoid cartilages.
• The space between vocal cords is called the glottis.

Larynx (Functions)

• Production of sound: pitch and volume are dependent on cord length and tension/force of air passed.
• Resonance: depends on shape of the mouth, tongue position, and paranasal sinuses.
• Protection of the lower respiratory tract: epiglottis closes the larynx during swallowing, preventing food from entering the trachea.
• Passageway for air: links pharynx and trachea

Trachea (Windpipe)

• Lies in front of the esophagus.
• About 10-11 cm long
• Extends from the larynx to the 5th thoracic vertebra.
• Divides into right and left primary bronchi.
• Structures associated with the trachea: larynx superiorly and inferiorly (right and left bronchi), isthmus of the thyroid gland anteriorly (upper part), arch of the aorta and sternum (lower portion), the esophagus posteriorly, and lungs and thyroid gland laterally.
• Composed of C-shaped cartilage rings, smooth muscle, and connective tissue.

Trachea (Structure/Functions)

• Flexible air duct with C-shaped cartilage rings to provide support and flexibility.

• Cartilages are incomplete posteriorly to allow esophagus expansion during swallowing.

• The smooth muscle in the posterior wall regulates the trachea's diameter.

• Ciliated mucus membrane captures and removes dust and debris.

• Cartilages held together by a connective tissue band (allows flexibility), posteriorly lacks cartilage to allow esophageal expansion in swallowing.

Bronchi

• Formed when trachea divides into two primary bronchi (right and left).
• The right is wider, shorter, and more vertical than the left.
• Enters the lung at the hilum (splits into smaller ones).
• Bronchi branch into lobar and segmental bronchi, which further branch into bronchioles.

Bronchial Passages (Changes)

• As bronchi divide, they become smaller, their cartilage structure changes to allow for greater airflow flexibility.
• Cartilage is not present in bronchioles, smooth muscles replace it.

Bronchial Contractility

• Smooth musculature in the bronchioles controls airflow by constriction or dilation.
• Under autonomic nervous system; parasympathetic input causes constriction and sympathetic input causes dilation.
• Important for regulating airflow and responding to environmental stimuli.

Alveoli

• Tiny air sacs in the lungs where gas exchange occurs.
• Composed of a single layer of squamous epithelial cells and a dense network of capillaries.
• The layer around the alveoli is called the respiratory membrane
• Gas exchange depends on diffusion driven by pressure differences in oxygen and carbon dioxide concentrations in air and blood.

Lungs

• Two spongy masses in the thorax, separated by the mediastinum.
• Right lung has three lobes; left lung has two lobes.
• Enclosed and separated by the pleura (thin tissue layers).
• Supported by the rib cage and separated from the abdomen by the diaphragm.

Pleural Cavity and Pleura

• Pleura: two layers (visceral and parietal) surrounding each lung forming a cavity.
• Pleural fluid lubricates the two layers to reduce friction during breathing.
• The space between the layers is the pleural cavity and contains no air.
• Surrounding a serosa.

External Respiration

• Oxygen diffuses from alveoli into pulmonary capillaries and CO2 diffuses from capillaries into alveoli.
• This exchange results in blood oxygen enrichment and CO2 removal.

Internal Respiration

• Blood (carrying oxygen) passes from capillaries to tissues, releasing oxygen in exchange for carbon dioxide.

Gas Transport in Bloodstream

• Oxygen (98.5%) is transported bound to hemoglobin, (1.5% dissolved in plasma).
• Carbon dioxide (70%) is transported as bicarbonate ions, (23% bound to hemoglobin, 7% as dissolved gas).

Respiration and the Lungs

• Breathing in (inspiration): muscles contract to increase thoracic volume, reducing pressure and drawing air into the lungs. – Active, energy required.
• Breathing out (expiration): muscles relax and thoracic volume decreases; increasing pressure expels air. – Passive, little energy required.

Variables Affecting Breathing

• Elasticity - lung ability to recoil to normal shape after inflation, important for breathing out
• Compliance - lung stretchability, important for breathing in, determined by the effort to create the necessary pressure.
• Airway Resistance - resistance caused by the airways during breathing, important for airflow. High resistance in conditions like bronchoconstriction necessitates higher effort.

Lung Volumes and Capacities

• Several measures are used to quantify the amount of air the lungs hold. This includes: Tidal Volume (TV): volume of air moved in and out during normal breathing. Inspiratory Reserve Volume (IRV): maximum extra air inhaled after a normal breath. Expiratory Reserve Volume (ERV): maximum extra air that can be exhaled after a normal breath. Residual Volume (RV): air remaining in lungs after maximum exhalation. Inspiratory Capacity (IC): Maximum volume that can be inhaled. Functional Residual Capacity (FRC): volume remaining in lungs after a normal breath. Vital Capacity (VC): maximum volume of air that can be moved in and out of the lungs during one respiratory cycle. Total Lung Capacity (TLC): total volume of air that the lungs can contain.

Explore the intricacies of the respiratory system, including its essential organs and their functions. This quiz will cover gas exchange, the structure of the nasal cavity, and the anatomy involved in the process of breathing. Prepare to test your knowledge on how the body utilizes oxygen and expels carbon dioxide.