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26 Anatomy of the Respiratory System

UNIT OUTLINE Functional Anatomy of the Respiratory System Activity 1: Exploring the Organs of the Respiratory System

Activity 2: Examining the Microscopic Anatomy of the Trachea and Lungs

Activity 3: Examining a Sheep Pluck

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he respiratory system provides the body with oxygen and rids it of carbon dioxide. It consists of two parts: the upper respiratory tract (nasal cavity, pharynx, and larynx) and the lower respiratory tract (trachea, bronchial tree, and lungs). In this unit you will study the anatomy of these structures; in Unit 27 you will explore respiratory physiology. T H I N K A B O U T I T Name a respiratory organ in which each of the following tissue types is predominant. Then, describe a function of the tissue type. Simple squamous epithelium ____________________________________________ ____________________________________________________________________ Hyaline cartilage _____________________________________________________ ____________________________________________________________________ Ciliated pseudostratified columnar epithelium ______________________________ ____________________________________________________________________ Smooth muscle ______________________________________________________ ____________________________________________________________________ ▪

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PRE-LAB ASSIGNMENTS

Pre-lab quizzes are also assignable in

To maximize learning, BEFORE your lab period carefully read this entire lab unit and complete these pre-lab assignments using your textbook, lecture notes, and prior knowledge.

P R E - L A B Activity 1: Exploring the Organs of the Respiratory System 1. Use the list of terms provided to label the accompanying figure showing the structures of the respiratory system. Check off each term as you label it. □ bronchi

□ left lung

□ alveoli

□ trachea

□ pharynx

□ diaphragm

□ larynx

□ lower respiratory tract

□ bronchiole

□ nasal cavity

□ right lung

□ upper respiratory tract

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2. Match each of the following respiratory organs with its correct description. _____

a. larynx

1. is a common passageway for respiratory and digestive systems

_____

b. nasal cavity

2. is composed of simple squamous epithelium

_____

c. bronchus

3. consists of two lobes

_____

d. pharynx

4. is composed of nine cartilaginous structures

_____

e. bronchiole

5. is innervated by the phrenic nerve

_____

f. right lung

6. leads into an alveolar duct

_____

g. alveolus

7. is divided into passageways called meatuses

_____

h. left lung

8. consists of three lobes

_____

i. diaphragm

9. branches from trachea

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U N I T 2 6 | Anatomy of the Respiratory System

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P R E - L A B Activity 2: Examining the Microscopic Anatomy of the Trachea and Lungs 1. Match each of the following structures with a predominant tissue type found in it. _____

a. supporting rings of trachea

1. ciliated pseudostratified columnar epithelium

_____

b. air sacs of lungs

2. simple squamous epithelium

_____

c. inner lining of trachea

3. smooth muscle

_____

d. submucosa of trachea

4. areolar connective tissue

_____

e. arterial wall

5. hyaline cartilage

2. How is the structure of the alveolus adapted to its function? ________________________________ _________________________________________________________________________________ 3. How is the structure of the trachea adapted to its function? _________________________________ _________________________________________________________________________________

P R E - L A B Activity 3: Examining a Sheep Pluck 1. What is a sheep pluck? _____________________________________________________________ ______________________________________________________________________________ 2. How will you inflate the lungs of the sheep pluck? ______________________________________ ______________________________________________________________________________

Functional Anatomy of the Respiratory System We will divide our study of the functional anatomy of the respiratory system into two parts: the upper respiratory tract and the lower respiratory tract.

The Upper Respiratory Tract The upper respiratory tract (Figure 26-1) consists of the nasal cavity, the pharynx, and the larynx. Air typically enters the nasal cavity through the anterior nares (nostrils). The nasal cavity (Figure 26-2) is divided into right and left sides by the nasal septum, a structure composed of both bone and cartilage (not visible in Figure 26-2). Three bony shelves—the superior, middle, and inferior nasal conchae—project from the lateral walls of the mucosa-lined nasal cavity and help to increase air turbulence, which aids in the warming, moistening, and filtering of incoming air.

The nasal cavity is separated from the oral cavity by the anterior hard palate and the posterior soft palate. When the soft palate is elevated during swallowing, an extension of it, called the uvula, helps to prevents food and liquids from entering the nasal cavity by closing off the posterior nares, the two posterior openings of the nasal cavity that lead to the pharynx (see Figure 26-2). Paranasal sinuses— air-filled cavities in the frontal, ethmoid, sphenoid, and maxillary bones that are continuous with the nasal cavity and are lined with mucous membranes—surround the nasal cavity. These sinuses reduce the weight of the skull, function as resonance chambers for speech, and warm and moisten incoming air. The pharynx is divided into three regions: the nasopharynx, which begins at the posterior nares and ends at the soft palate; the oropharynx, which begins at the soft palate and ends at the superior margin of the epiglottis; and the laryngopharynx, which begins at the superior margin of the epiglottis and ends at the cricoid cartilage of the larynx, where it becomes continuous with the esophagus

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U N I T 2 6 | Anatomy of the Respiratory System

Nose Nasal cavity

Pharynx

Upper respiratory tract

Larynx

Left lung Right lung

Trachea

Thoracic cage (cut) Bronchi

Thoracic cavity

Lower respiratory tract

Diaphragm

Bronchiole Alveoli

Figure 26-1 Structures of the respiratory system.

(see Figure 26-2). The pharynx conducts air to the larynx and food and fluids to the esophagus. The larynx, which is located inferior to the laryngopharynx, consists of three paired cartilages and three single cartilages held together by laryngeal ligaments (Figure 26-3). All of these cartilaginous structures except the epiglottis are composed of hyaline cartilage. The three smaller, paired cartilages—the arytenoid, cuneiform, and corniculate cartilages—are located in the posterior and lateral walls of the larynx. The three single cartilages form the body of the larynx. The largest—the thyroid cartilage—contains an anterior laryngeal prominence commonly referred to as the Adam’s apple. The cricoid cartilage, located inferior to the thyroid cartilage, is ring shaped; it is the only cartilage in the larynx or trachea that forms a complete ring. During swallowing, the epiglottis, a flap-like structure composed of elastic cartilage,

forms a lid over the glottis, the slit-like opening that allows air into the larynx. The epiglottis is often referred to as the “guardian of the airways.” Lateral to the glottis are two pairs of folds commonly called the “vocal cords.” The superior vestibular folds, known as the false vocal cords, prevent foreign materials from entering the glottis; the inferior vocal folds, known as the true vocal cords, vibrate to produce speech.

The Lower Respiratory Tract The lower respiratory tract (see Figure 26-1) consists of the trachea (commonly called the windpipe) and its branches, and the lungs. The trachea (Figure 26-4) is a tubular structure that conducts air from the larynx to the bronchi. The trachea is supported by C-shaped cartilaginous rings that keep the airway open. The mucosa of the trachea is lined with

U N I T 2 6 | Anatomy of the Respiratory System Nasal meatuses: Superior

Frontal sinus Sphenoid sinus

Nasal conchae: Superior

Middle

Middle

Inferior

Inferior

Posterior naris

Nasal cavity

Oral cavity Nasopharynx

Uvula Tongue

Oropharynx Epiglottis Laryngopharynx Larynx Vestibular fold Esophagus

Vocal fold

(a) Illustration showing structures of the upper respiratory system

Nasal meatuses:

Nasal conchae:

Superior

Superior

Middle

Middle

Inferior

Inferior

Nasal cavity Posterior naris

Oral cavity

Nasopharynx Uvula

Oropharynx

Tongue

Laryngopharynx

Epiglottis

Esophagus

Larynx Vestibular fold Vocal fold

(b) Photo showing structures of the upper respiratory system

Figure 26-2 A sagittal section of the nasal cavity and the upper respiratory tract.

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Epiglottis

Hyoid bone

Hyoid bone Adipose tissue Thyroid cartilage

Thyroid cartilage

Corniculate cartilage Arytenoid cartilage

Cricothyroid ligament

Cricoid cartilage

Cricoid cartilage Cartilage of trachea

(a) Anterolateral view

Vestibular fold Vocal fold

Cartilage of trachea

Esophagus (b) Posterior view

(c) Midsagittal section

Figure 26-3 The larynx. Posterior Esophagus Larynx Mucosa Submucosa Trachea

Smooth muscle

Lumen of trachea Adventitia

Carina Primary bronchi

Cartilaginous ring (hyaline cartilage)

Anterior Mucosa

(b) Cross section through trachea and esophagus

Submucosa

(a) Trachea and lungs

Hyaline cartilage LM (250×) (c) Light micrograph of tracheal tissue layers

Figure 26-4 The trachea.

U N I T 2 6 | Anatomy of the Respiratory System

ciliated pseudostratified columnar epithelium containing many mucus-secreting goblet cells. The mucus traps dust, bacteria, and other foreign matter, and the cilia propel the mucus upward to the throat so that it can be coughed up or swallowed. At its inferior end the trachea branches at a ridge, called the carina, into the left and right primary bronchi, which enter the lungs. As the primary bronchi enter the lungs, they branch into secondary bronchi and then into tertiary bronchi, forming a structure known as the bronchial tree (Figure 26-5). The

Trachea Right primary bronchus

Left primary bronchus

Right secondary bronchi

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tertiary bronchi branch repeatedly into smaller and smaller bronchi that eventually branch into bronchioles. Bronchioles further branch into terminal bronchioles, which branch into respiratory bronchioles. The point at which the terminal bronchioles branch into respiratory bronchioles marks the border between the conducting zone, which consists of the respiratory passageways from the nasal cavity to the terminal bronchioles, and the respiratory zone, which also includes the alveolar ducts and alveolar sacs (Figure 26-6). The conducting zone is so named because it conducts air to and from the respiratory zone. Respiratory bronchioles divide into alveolar ducts that lead into clusters of alveoli called alveolar sacs. Each alveolar sac consists of individual alveoli (air sacs) and their overlying pulmonary capillaries. Together the alveoli and pulmonary capillaries make up the respiratory membrane, where gas exchange takes place.

Left secondary bronchi

Right tertiary bronchi

Left tertiary bronchi

Figure 26-5 The bronchial tree. Terminal bronchiole

Pulmonary venule

Respiratory bronchiole

Alveolar duct

Pulmonary capillaries

Elastic fibers Pulmonary arteriole

Alveolar sac Smooth muscle Alveoli

Conducting zone

Figure 26-6 Structures of the respiratory zone.

Respiratory zone

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U N I T 2 6 | Anatomy of the Respiratory System

Apex of lung

Clavicle Mediastinum

Pleural cavity

Right superior lobe

Left superior lobe

Horizontal fissure Right middle lobe

Cardiac notch

Right oblique fissure

Left oblique fissure

Right inferior lobe

Left inferior lobe Base of lung

Diaphragm

Figure 26-7 The lungs.

As the bronchial tree branches from the primary bronchi to the respiratory bronchioles, the amount of cartilage in the respiratory tubes decreases, and the amount of smooth muscle increases. The epithelium lining the respiratory tubes also changes: from pseudostratified columnar epithelium in the primary bronchi, to columnar epithelium in the smaller bronchi, to cuboidal epithelium in the bronchioles, to simple squamous epithelium in the alveoli. The lungs, which are located within the thoracic cavity, are paired cone-shaped organs (Figure 26-7) that are surrounded by a double-layered serous membrane. The outer layer, the parietal pleura, is attached to the wall of the thoracic cavity and the diaphragm. The inner layer, the visceral pleura, covers the surface of each lung. Between these two layers is the pleural cavity, which is filled with a serous fluid. The right lung is divided into three lobes (the superior, middle, and inferior lobes) that are separated by an oblique fissure and a horizontal fissure. The left lung is divided into two lobes (the superior and inferior lobes) separated by an oblique fissure. The left lung also has an indention called the cardiac notch where the apex of the heart sits.

ACTIVITY

1

Exploring the Organs of the Respiratory System Learning Outcomes 1. Identify the organs of the respiratory tract, and describe the functions of each organ. 2. For each respiratory organ, describe the structural adaptations that enable it to perform its functions.

Materials Needed □ Torso model or other anatomical models □ Anatomical charts Instructions CHART As you complete the following Making Connections chart, locate each respiratory structure on an anatomical model or chart and identify its anatomical features. Then review its description and/or function(s). Finally, make some “connections” to things you’ve already learned in your lectures, in your assigned reading, and in your lab. Some portions of the chart have been filled in as examples.

Optional Activity ™

Practice labeling respiratory organs on human cadavers at > Study Area > Practice Anatomy Lab > Human Cadaver > Respiratory System

U N I T 2 6 | Anatomy of the Respiratory System

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Making Connections: Organs of the Respiratory System Respiratory Structure

Description (Structure and/or Function)

Nasal cavity

Connections to Things I Have Already Learned Nasal conchae with meatuses cause air turbulence to warm and moisten air more efficiently; olfactory nerve fibers of the olfactory nerve (CN I) pass through the olfactory foramina of the cribriform plate of the ethmoid bone.

Paranasal sinuses

Pharynx

Larynx

Passageway for air; contains vocal folds, which produce sound; epiglottis prevents food and fluids from entering airways.

Trachea

Bronchi

Bronchitis = inflammation of the mucous membrane lining the bronchial passages.

Bronchiole

(Continued)

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Making Connections: Organs of the Respiratory System (Continued) Respiratory Structure

Description (Structure and/or Function)

Lungs

Contain alveoli; site of gas exchange.

Connections to Things I Have Already Learned

Blood supply

Pulmonary arteries branch from pulmonary trunk, which arises from RV of heart; pulmonary capillaries wrap around each alveolus to form respiratory membrane; pulmonary vein returns oxygenated blood to LA of heart; bronchial artery arises from thoracic aorta.

Breathing muscles

Diaphragm is innervated by phrenic nerve; intercostal muscles are innervated by intercostal nerves, which arise from ventral rami of T2–T12.

ACTIVITY

2

Examining the Microscopic Anatomy of the Trachea and Lungs

pattern that we see in many hollow organs: an innermost mucosa, a middle submucosa, and an outermost adventitia. Sketch and label these three layers of the trachea.

Learning Outcomes 1. Observe a histological section of the trachea; then identify the following structures and describe the function of each: pseudostratified columnar epithelium, cilia, goblet cell, and hyaline cartilage. 2. Observe a histological section of the lung; then identify the following structures and describe the function of each: bronchiole, alveolar duct, alveolar sac, and alveolus.

Materials Needed □ Microscope and slides (or photomicrographs) of trachea and lung Instructions 1. Observe a histological slide (or a photomicrograph) of the trachea under low power. Note the distinct histological

Total magnification: _____ ×

U N I T 2 6 | Anatomy of the Respiratory System

2. Switch to the high-power objective (or view a higherpower photomicrograph) and observe the tissues found in the mucosa and the submucosa.

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5. Label each of the following structures on Figure 26-8: alveolar ducts, alveolar sac, alveolus, artery, bronchiole

_____________________________________________

6. Now, observe the lung slide using the oil-immersion objective (or view a photomicrograph provided by your instructor). Identify an alveolus.

Identify a goblet cell and state its function. ____________

What is the function of an alveolus? ________________

_____________________________________________

_____________________________________________

Identify cilia and state their function. _________________

Which tissue type comprises the alveolar wall?

_____________________________________________

_____________________________________________

Which tissue type is predominant in the mucosa?

The epithelial tissue is separated from underlying connective tissue by which structure? ________________________ _____________________________________________ Which tissue types are prominent in the submucosa? ________________________...