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Questions and Answers
What is one of the main functions of Clara cells in the terminal bronchioles?
What is one of the main functions of Clara cells in the terminal bronchioles?
Which statement accurately describes the difference between bronchi and bronchioles?
Which statement accurately describes the difference between bronchi and bronchioles?
How does the smooth muscle layer function in bronchioles during expiration?
How does the smooth muscle layer function in bronchioles during expiration?
What role does the adventitia play in the structure of bronchioles?
What role does the adventitia play in the structure of bronchioles?
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Which statement about respiratory bronchioles is true?
Which statement about respiratory bronchioles is true?
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What is the primary nervous system control over bronchiolar smooth muscles?
What is the primary nervous system control over bronchiolar smooth muscles?
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Which cell type decreases in height and cilia as the bronchiole gets smaller?
Which cell type decreases in height and cilia as the bronchiole gets smaller?
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What treatment is commonly used to relieve bronchial asthma by relaxing bronchiolar smooth muscle?
What treatment is commonly used to relieve bronchial asthma by relaxing bronchiolar smooth muscle?
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What type of epithelium is found in the trachea?
What type of epithelium is found in the trachea?
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Which feature is characteristic of intrapulmonary bronchi?
Which feature is characteristic of intrapulmonary bronchi?
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What condition can result from immotility of cilia?
What condition can result from immotility of cilia?
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What is the role of Clara cells in the bronchioles?
What is the role of Clara cells in the bronchioles?
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Which component is absent in the submucosa of intrapulmonary bronchi?
Which component is absent in the submucosa of intrapulmonary bronchi?
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What anatomical characteristic differentiates the trachea from intrapulmonary bronchi?
What anatomical characteristic differentiates the trachea from intrapulmonary bronchi?
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How do the ciliated cells change along the bronchiole's length?
How do the ciliated cells change along the bronchiole's length?
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What is a primary function of the respiratory epithelium under irritant exposure?
What is a primary function of the respiratory epithelium under irritant exposure?
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Where are sebaceous glands most abundant?
Where are sebaceous glands most abundant?
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What type of secretion do sebaceous glands produce?
What type of secretion do sebaceous glands produce?
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What initiates the secretion of sebaceous glands?
What initiates the secretion of sebaceous glands?
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What is the primary function of sebum?
What is the primary function of sebum?
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Which of the following regions may have sebaceous ducts opening directly onto the epidermal surface?
Which of the following regions may have sebaceous ducts opening directly onto the epidermal surface?
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What results from the degeneration of large rounded cells in sebaceous glands?
What results from the degeneration of large rounded cells in sebaceous glands?
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What characterizes the anatomical structure of sebaceous glands?
What characterizes the anatomical structure of sebaceous glands?
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What condition is characterized by chronic inflammation of sebaceous glands?
What condition is characterized by chronic inflammation of sebaceous glands?
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What is the primary function of clear cells in the glands described?
What is the primary function of clear cells in the glands described?
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Which statement accurately describes the dark cells in the glands?
Which statement accurately describes the dark cells in the glands?
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What surrounds the myoepithelial cells in the gland structure?
What surrounds the myoepithelial cells in the gland structure?
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How do the ducts of apocrine glands differ from eccrine glands?
How do the ducts of apocrine glands differ from eccrine glands?
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What type of secretion are apocrine glands known for?
What type of secretion are apocrine glands known for?
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What characterizes the epithelial lining of the excretory duct in the glands?
What characterizes the epithelial lining of the excretory duct in the glands?
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Where are sebaceous glands predominantly located?
Where are sebaceous glands predominantly located?
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What is a key difference between eccrine sweat glands and apocrine sweat glands?
What is a key difference between eccrine sweat glands and apocrine sweat glands?
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What is the origin of melanocytes?
What is the origin of melanocytes?
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Which enzyme is crucial for melanin formation in melanocytes?
Which enzyme is crucial for melanin formation in melanocytes?
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What condition is associated with the absence of the tyrosinase enzyme?
What condition is associated with the absence of the tyrosinase enzyme?
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What is the primary function of Langerhans cells?
What is the primary function of Langerhans cells?
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Merkel's cells are primarily associated with which type of sensory function?
Merkel's cells are primarily associated with which type of sensory function?
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The dermis consists of which two layers?
The dermis consists of which two layers?
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How are Langerhans cells connected to keratinocytes?
How are Langerhans cells connected to keratinocytes?
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What triggers hyperpigmentation in Addison's disease?
What triggers hyperpigmentation in Addison's disease?
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Study Notes
Trachea/Extrapulmonary Intrapulmonary Bronchi
- The Trachea and Bronchi differ in lumen size, mucosa folding, and composition of epithelial cells, elastic membranes, and muscle layers.
- The trachea has a wide lumen, less folded mucosa with pseudostratified columnar ciliated epithelium containing goblet cells, an elastic membrane in the mucosa, a present submucosa, and smooth muscle extending between the cartilaginous rings.
- The intrapulmonary bronchi have a narrow lumen, highly folded mucosa with pseudostratified columnar ciliated epithelium containing few goblet cells, no elastic membrane but elastic fibers in lamina propria, an absent submucosa, and spirally arranged smooth muscle fibers surrounding the mucosa.
Clinical Hints
- Chronic exposure to irritants like cigarette smoke or coal dust can lead to metaplasia in the respiratory epithelium, resulting in an increase in goblet cells relative to ciliated cells.
- Immotile cilia syndrome causes immotile spermatozoa and infertility in men and chronic respiratory-tract infections in both sexes due to immobility of cilia and flagella.
- This syndrome is often caused by deficiency of dynein, a protein found in cilia, which participates in ciliary movement and has ATPase activity.
Bronchioles
- Bronchioles are airways smaller than 1 mm in diameter and are composed of a mucosa, musculosa, and adventitia.
- The mucosa of bronchioles consists of simple columnar ciliated epithelium containing Clara cells, which increase in number as the bronchiole gets smaller and ciliated cells decrease.
- Clara cells are dome-shaped, non-ciliated cells with secretory granules that function in surfactant secretion, protection of bronchiolar epithelium, detoxification, and stem cell activity.
- The musculosa of bronchioles contains circularly arranged smooth muscles.
- The adventitia of bronchioles is composed of connective tissue without glands, cartilage, or lymphatic nodules.
Terminal Bronchioles
- Terminal bronchioles are the last part of the conducting portion of the respiratory system and are lined with cubical ciliated cells and Clara cells.
Differences between Bronchus and Bronchiole
- The bronchus has less folded mucosa lined by pseudostratified columnar ciliated epithelium with goblet cells, less developed spirally smooth muscle, cartilage plates, lymphatic nodules, and mucoserous glands in the adventitia.
- The bronchiole has a highly folded mucosa lined by simple columnar ciliated epithelium with Clara cells, more developed circularly smooth muscle, no cartilage plates, no lymphatic nodules, and no mucoserous glands in the adventitia.
Clinical Hints
- The smooth muscle layers of bronchioles are controlled by the parasympathetic nervous system.
- During expiration, smooth muscle contraction leads to air expulsion, while relaxation occurs during inspiration.
- In bronchial asthma, prolonged smooth muscle contraction during expiration makes air expulsion difficult.
- Steroids and β2-agonists can relax bronchiolar smooth muscle and are used to relieve asthmatic attacks.
Respiratory Portion - Respiratory Bronchioles
- Respiratory bronchioles connect the conducting portion to the respiratory portion of the respiratory system and are involved in both air conduction and gas exchange.
Langerhans Cells
- Langerhans cells are antigen-presenting cells located in the upper stratum spinosum of the epidermis.
- They arise from bone marrow precursors and migrate into the epidermis via the blood.
- They are not attached to surrounding keratinocytes by desmosomes and have long slender processes radiating between keratinocytes.
- Their function is to participate in the body's immune responses and protect the skin against infections.
Merkel's Cells
- Merkel's cells are modified epidermal cells involved in sensory reception, located in the basal layer of the epidermis of both thick and thin skin.
- They are attached to basal cells by desmosomes and are closely associated with sensory nerve fibers.
- The nerve fiber terminates as a disc-like expansion under the Merkel's cell, forming a Merkel's tactile corpuscle, which acts as a sensitive mechanoreceptor for light touch.
Dermis (Corium)
- The dermis is a connective tissue layer that supports the epidermis and binds it to the subcutaneous tissue.
- It is thicker than the epidermis and has projections called dermal papillae that fit into concavities in the epidermis.
- It consists of two layers: the papillary layer and the reticular layer.
Sweat Glands
- Sweat glands are simple coiled tubular glands located deep in the dermis.
- They are composed of three cell types: clear cells, dark cells, and myoepithelial cells.
- Clear cells are larger and more numerous than dark cells and secrete sodium chloride, urea, uric acids, ammonia, and water.
- Dark cells are smaller and less numerous than clear cells and secrete glycoproteins.
- Myoepithelial cells are spindle-shaped and help in squeezing secretion from the gland.
- The excretory duct of sweat glands is lined by two layers of cuboidal cells and opens onto the epidermal surface.
Apocrine Sweat Glands
- Apocrine sweat glands are enlarged, modified eccrine sweat glands found in the axilla, areola of the breast, pubic region, and anal region.
- They are less numerous than eccrine glands and have larger secretory portions with wider lumen.
- Their secretory portion is mainly composed of dark cells with numerous secretory granules.
- They open into the upper part of hair follicles.
- Their secretion is initially odorless but acquires an odor due to bacterial activity.
- They become functional at puberty.
Sebaceous Glands
- Sebaceous glands are simple acinar or simple branched acinar glands found in the dermis over most of the body, except in palms and soles.
- They are most abundant on the face, scalp, and forehead.
- They secrete sebum, a mixture of lipids that keeps the skin and hair soft and prevents dryness.
- Secretion begins at puberty and is influenced by sex hormones.
Clinical Hints
- Acne is a chronic inflammation of sebaceous glands caused by obstruction of the duct by sebum impaction or disturbance in normal secretion.
- It is more severe in boys during and after puberty due to increased sex hormone levels.
Comparison between Sweat Glands and Sebaceous Glands
- Sweat glands are found in both hairy and non-hairy skin, while sebaceous glands are found only in hairy skin.
- Sweat glands are found deep in the dermis, while sebaceous glands are found in the superficial part of the dermis.
- Sweat glands are simple coiled tubular glands, while sebaceous glands are simple alveolar or simple branched alveolar glands.
- Both eccrine and apocrine sweat glands secrete by merocrine (no loss of cellular structure), while sebaceous gland secretion is holocrine (involves loss of cellular structure).
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Description
Test your knowledge on the anatomical differences between the trachea and bronchi. This quiz covers aspects such as lumen size, mucosa structure, and epithelial cell composition. Additionally, explore clinical implications related to respiratory epithelium changes due to chronic irritant exposure.
