Introduction to the Respiratory Tract

Introduction and Functions of the Respiratory Tract

• The respiratory tract functions to bring oxygen into the body and remove carbon dioxide.
• It can be divided into upper and lower respiratory tracts.

Anatomy of the Respiratory Tract

• The respiratory tract consists of the nose, pharynx, larynx, trachea, and lungs.

Nose

• The nose consists of an external and internal part.
• External Nose is pyramidal in shape.
  • It includes the tip, root, dorsum, and nostrils.
  • The two nostrils are called nares.
    • They are pear-shaped openings.
    • The nasal septum divides the nostrils.
    • Ala of the nose is the lateral aspect.
• Nasal Cavity: The cavity is divided in half by the nasal septum.
  • The nasal cavity extends from the nostrils to the choanae openings.
  • Vestibule: is closest to the nostrils and is lined with hair and sebaceous glands.
  • Nasal Cavity Proper: Lined with respiratory epithelium.
    • The respiratory epithelium contains cilia.
    • The cilia help to move mucus toward the nasopharynx.

Nasal Cavity – Divisions & Structure

• The nasal cavity is divided into two halves, and each half is further divided into four sections:
  • Roof
    • 7 cm long and 2 mm wide.
    • Formed by the ethmoid (cribriform plate), frontal bone, nasal bones, nasal cartilages, and sphenoid bone.
  • Floor
    • 5 cm long and 1.5 cm wide.
    • Formed by the palatine process of maxilla and horizontal plate of the palatine bone.
  • Medial Wall - Formed by the nasal septum.
  • Lateral Wall
    • Contains three nasal conchae (superior, middle, inferior).
      • The conchae create turbulence in the air flow, which helps to warm, moisten, and filter the air.
      • They also increase the surface area of the nasal cavity, which improves the sense of smell.
    • Each concha forms a corresponding nasal meatus:
      • Inferior Meatus: Formed by the inferior concha and the floor of the nasal cavity. The nasolacrimal duct opens here.
      • Middle Meatus: Formed by the middle concha. The frontal sinus, maxillary sinus, and anterior/middle ethmoid sinuses drain here.
      • Superior Meatus: Formed by the superior concha. The posterior ethmoid sinuses drain here.
      • Supreme Meatus: Between the superior concha and the roof. The sphenoidal sinus drains here.
      • Sphenoethmoidal Recess: A depression above the superior concha. It is the opening to the sphenoidal sinuses.

Nasal Cavity - Dimensions

• Nasal cavity dimensions are:
  • Height: 5 cm
  • Length: 5-7 cm
  • Width: 1.5 cm near the floor and 1-2 mm near the roof.

Nasal Cavity - Blood Supply and Innervation

• Arteries:
  • Dorsal nasal branch (ophthalmic)
  • Infraorbital (maxillary)
  • Alar and Septal (facial)
• Nerves:
  • Sensory:
    • External nasal, Alar, Septal (all branches of the facial nerve)
    • Infratrochlear (ophthalmic)
    • Infraorbital (maxillary)
  • Motor:
    • Facial nerve branches

Lateral Wall of the Nose

• Blood Supply:
  • Anterior Ethmoidal
  • Posterior Ethmoidal
  • Sphenopalatine
  • Facial
  • Greater Palatine
• Nerve Supply:
  • Sensory:
    • Anterior ethmoidal (ophthalmic)
    • Anterior superior alveolar (maxillary)
    • Posterior superior lateral nasal (pterygopalatine ganglion)
    • Anterior palatine (pterygopalatine ganglion)
  • Special Sensory:
    • Olfactory Nerve (responsible for smell)

Applied Anatomy of the Nose

• Septal Deviation:
  • A deviated septum is a common condition. It causes congestion and obstruction.
  • Treatment is done by submucosal resection of the nasal septum.
• Epistaxis (Nosebleeds):
  • A common condition, especially in Kiesselbach's area (aka Little's area). Kiesselbach's area is an area of anastomosis between the four main nasal arteries and is located in the anteroinferior part of the nasal septum.
• Dangerous Area:
  • Infection in this area can spread to the cranial cavity along the olfactory nerves.
• Nasal Fracture:
  • A break in the bone or cartilage of the nose. Most often occurs over the bridge of the nose or the nasal septum.
• Nasal Polyps:
  • Benign, soft, non-cancerous growths in the nasal cavity.
• Allergic Rhinitis:
  • Inflammation and swelling of the nasal mucosa, especially in the inferior nasal concha. Can block the nasal passages.

Pharynx

• The pharynx is a musculomembranous tube that extends from the cranial base to the lower border of the cricoid cartilage.
• It is located behind and communicates with the nasal, oral, and laryngeal cavities.
• The pharynx is divided into three regions:
  • Nasopharynx: Connects the nasal cavity to the pharynx.
  • Oropharynx: Connects the oral cavity to the pharynx.
  • Laryngopharynx: Connects the larynx to the pharynx.

Nasopharynx

• Structures:
  • Auditory tube opening: Connects the middle ear to the nasopharynx.
  • Tubal elevation: A projection that surrounds the auditory tube opening.
  • Salpingopharyngeal and salpingopalatine folds: Folds of tissue extending from the tube to the pharyngeal wall and palate.
  • Tubal tonsils: Lymphoid tissue located near the auditory tube opening.
  • Pharyngeal tonsils (adenoids): Lymphoid tissue located at the posterior wall of the nasopharynx.

Oropharynx

• Structures:
  • Palatopharyngeal folds (arches): Folds extending from the soft palate to the pharynx.
  • Palatine tonsils: Lymphoid tissue in the oropharynx.
  • Tonsillar fossa: A shallow recess between the palatine tonsils.

Laryngopharynx

• Structures:
  • The inlet of the larynx.
  • The posterior wall.

Pharynx - Wall

• Muscle Wall:
  • Formed by skeletal muscles and fascia.
  • Buccopharyngeal fascia: Lines the outside of the muscle wall.
  • Pharyngobasilar fascia: Lines the inside of the muscle wall.

Muscles of the Pharynx

• Constrictors
  • Superior, Middle, and Inferior Constrictors: All originate behind the nasal, oral, and laryngeal cavities.
    • They meet on the midline raphe.
• Longitudinal Muscles
  • Stylopharyngeus:
  • Palatopharyngeus:
  • Salpingopharyngeus:

Nerve Supply of Pharynx

• All constrictors and salpingopharyngeus muscles are supplied by the pharyngeal branch of the vagus nerve.
• Stylopharyngeus is supplied by the glossopharyngeal.
• Palatopharyngeus is supplied by the cranial part of the accessory nerve.

Blood Vessels and Lymphatic System of Pharynx

• Arteries:
  • Ascending pharyngeal
  • Lingual
  • Facial
  • Maxillary
• Veins:
  • Venous plexus surrounds the pharynx and drains into the internal jugular and facial veins.
• Lymphatics:
  • Drain into the deep cervical lymph nodes.

Nerve Supply of Pharynx

• Pharyngeal plexus is formed by three nerves
  • Glossopharyngeal
  • Vagus
  • Cranial Accessory

Killian’s Dehiscence

• A triangular area in the pharyngeal wall that is a potential weak spot for the development of Zenker's diverticulum.
• It is found between the thyropharyngeal and cricopharyngeus muscles.

Paranasal Air Sinuses

• Air-filled spaces in the bones surrounding the nasal cavity.
• They are named after the bones in which they are located.
• The four groups of sinuses:
  • Maxillary: are aerated at birth
  • Ethmoid: develop during puberty
  • Frontal: 6-7 years
  • Sphenoid: 6-7 years
• The paranasal sinuses are lined with pseudostratified ciliated columnar epithelium and communicate with the nasal cavity through relatively small apertures.

Functions of the Paranasal Air Sinuses

• They decrease the weight of the skull.
• They warm, moisten, and filter incoming air.
• They serve as resonating chambers for the voice.
• They act as shock absorbers in trauma.
• They may help control the immune system.
• They may change vocal quality when blocked or filled with fluid.

Applied Anatomy of the Paranasal Air Sinuses

• Sinusitis: Inflammation or swelling of the sinus tissue.
  • Healthy sinuses are filled with air, but when they become blocked they can become infected.
  • Common cold, allergic rhinitis, nasal polyps, and deviated nasal septum can also cause sinusitis.

Introduction

• The respiratory tract is a vital system responsible for gas exchange.
• It is divided into upper and lower sections.
• The upper respiratory tract comprises the nose, pharynx, larynx, and trachea.

Nose

• The external nose has a pyramidal shape with distinct parts, including: apex, root, dorsum, and nostrils.
• The nasal cavity is divided into two halves by the nasal septum, a structure composed of bone and cartilage.
• The vestibule, located near the nostrils, is lined by skin and contains hairs called vibrissae.
• The nasal cavity itself is lined by mucous membrane for filtration and humidity control.
• The nasal septum is formed by the perpendicular plate of the ethmoid bone, vomer, septal cartilage, and inferior nasal cartilage.

Nasal Cavity Structure

• The roof of the nasal cavity is 7cm long and 2mm wide, sloping downwards both in front and behind.
• The roof is formed by the cribriform plate of the ethmoid bone, the nasal part of the frontal bone, nasal bones, nasal cartilages and the inferior surface of the body of the sphenoid bone.
• The floor is 5cm long and 1.5cm wide, formed by the palatine process of the maxilla and the horizontal plate of the palatine bone.
• The lateral wall of the nasal cavity is composed of the concha and meatuses.

Concha and Meatuses

• The inferior, middle, and superior concha are three bony structures that project into the nasal cavity.
• They divide the nasal cavity into spaces called meatuses, each associated with specific openings or spaces.
• Each meatus has both an inner and outer wall. The inner wall is formed by the concha themselves (and is comprised of the bone). The outer wall is made from the specific bones that each meatus sits within.

Lateral Wall of the Nose

• The lateral wall of the nose is subdivided into the vestibule, atrium of the middle meatus, and the concha.
• The spaces between the concha are called meatuses, which are important for airflow and drainage.

Blood Supply and Innervation

• The nose is supplied by branches of the ophthalmic, maxillary, and facial arteries.
• Innervation is provided by branches of the ophthalmic and maxillary nerves, with sensory and motor components.

Pharynx

• The pharynx is a 12-14 cm long musculomembranous tube extending from the cranial base to the level of the sixth cervical vertebra.
• It is divided into nasopharynx, oropharynx, and laryngopharynx.
• The pharynx lies behind and communicates with the nasal, oral and laryngeal cavities.
• The oropharyngeal isthmus connects the oral cavity and pharynx.

Muscles of the Pharynx

• Three constrictors (superior, middle, inferior) along with three longitudinal muscles (stylopharyngeus, palatopharyngeus, salpingopharyngeus) comprise the muscles of the pharynx.
• The constrictors originate posterior to the nasal, oral, and laryngeal cavities, meeting at midline raphe.
• The longitudinal muscles play a role in swallowing and speech.

Nerve Supply

• The pharynx is innervated by the pharyngeal plexus, formed by branches of the glossopharyngeal, vagus, and cranial accessory nerves.
• The pharyngeal branch of the vagus nerve supplies the constrictors and salpingopharyngeus, while the glossopharyngeal nerve supplies the stylopharyngeus, and the cranial part of the accessory nerve supplies the palatopharyngeus.

Paranasal Sinuses

• These are air-filled cavities found in the bones surrounding the nasal cavity.
• The four main groups are: maxillary sinuses (Antrum of Highmore), ethmoid sinuses, frontal sinus, and sphenoid sinus.
• They are lined with mucoperiosteum and filled with air, communicating with the nasal cavity through small apertures.
• The sinuses are lined by pseudostratified ciliated columnar epithelium.

Killian's Dehiscence

• This is a triangular area in the wall of the pharynx between the thyropharyngeal and cricopharyngeus muscles.
• It represents a potentially weak spot where a pharyngoesophageal diverticulum (Zenker's diverticulum) may occur.

Applied Anatomy

• Septal deviation of the nasal septum can cause congestion and obstruction, often requiring corrective surgery.
• Epistaxis, bleeding from the nose, can be a concern, especially in Kiesselbach's plexus, a common site of bleeding in the anteroinferior part of the nasal septum.
• Fractures of the nasal bones, often referred to as a broken nose, are common injuries.
• Nasal polyps are benign growths in the nasal cavity.
• Allergic rhinitis can lead to hypertrophy of the mucosa over the inferior nasal concha.
• Infections can spread from the nasal cavity to the middle cranial fossa through the cribriform plate, or to the lacrimal apparatus via the nasolacrimal duct.

Explore the anatomy and functions of the respiratory tract, including its division into upper and lower parts. Delve into specific structures like the nose and nasal cavity, learning about their roles in respiration.