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Which of the following glands are primarily formed of numerous cells?
Which of the following glands are primarily formed of numerous cells?
Which type of gland secretion is known for being watery and rich in enzymes?
Which type of gland secretion is known for being watery and rich in enzymes?
What secretion type is characteristic of both submandibular and sublingual glands?
What secretion type is characteristic of both submandibular and sublingual glands?
Which gland secretion method involves the entire cell and its contents being released?
Which gland secretion method involves the entire cell and its contents being released?
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Which of the following glands are formed of a single cell type?
Which of the following glands are formed of a single cell type?
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What is one of the primary functions of epithelial tissue?
What is one of the primary functions of epithelial tissue?
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Which characteristic describes the cellular arrangement of epithelial tissue?
Which characteristic describes the cellular arrangement of epithelial tissue?
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Which type of epithelial tissue has multiple layers of cells?
Which type of epithelial tissue has multiple layers of cells?
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What feature distinguishes simple epithelial tissues from stratified ones?
What feature distinguishes simple epithelial tissues from stratified ones?
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What is the primary purpose of the basement membrane in epithelial tissues?
What is the primary purpose of the basement membrane in epithelial tissues?
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Which type of epithelium is specialized for secretion and forms glands?
Which type of epithelium is specialized for secretion and forms glands?
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How does the epithelial tissue regenerate?
How does the epithelial tissue regenerate?
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What is a unique characteristic of pseudostratified columnar epithelium?
What is a unique characteristic of pseudostratified columnar epithelium?
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What characteristic is unique to transitional epithelium?
What characteristic is unique to transitional epithelium?
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How does the number of layers in transitional epithelium change when the bladder is full?
How does the number of layers in transitional epithelium change when the bladder is full?
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Which of the following is NOT a location where transitional epithelium is found?
Which of the following is NOT a location where transitional epithelium is found?
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What type of glands are formed by cells specialized to secrete substances?
What type of glands are formed by cells specialized to secrete substances?
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Which substance is typically found between the cells in transitional epithelium?
Which substance is typically found between the cells in transitional epithelium?
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Which gland secretes hormones directly into the bloodstream?
Which gland secretes hormones directly into the bloodstream?
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What is a characteristic feature of cells in glandular epithelia?
What is a characteristic feature of cells in glandular epithelia?
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What is the typical function of large ducts of salivary glands?
What is the typical function of large ducts of salivary glands?
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Which type of epithelium is characterized by a monolayer of crowded columnar cells with oval nuclei at different levels?
Which type of epithelium is characterized by a monolayer of crowded columnar cells with oval nuclei at different levels?
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Where is simple columnar absorptive epithelium primarily found?
Where is simple columnar absorptive epithelium primarily found?
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What distinguishes pseudostratified columnar epithelium with motile cilia from non-motile ciliated forms?
What distinguishes pseudostratified columnar epithelium with motile cilia from non-motile ciliated forms?
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In which anatomical location would you most likely find stratified squamous non-keratinized epithelium?
In which anatomical location would you most likely find stratified squamous non-keratinized epithelium?
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What feature is unique to simple columnar ciliated epithelium found in bronchioles?
What feature is unique to simple columnar ciliated epithelium found in bronchioles?
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What is the primary function of the keratinized layer in stratified squamous epithelium?
What is the primary function of the keratinized layer in stratified squamous epithelium?
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Which of the following structures does NOT contain pseudostratified columnar epithelium with motile cilia?
Which of the following structures does NOT contain pseudostratified columnar epithelium with motile cilia?
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Which type of epithelium covers the oral cavity and is important for protection?
Which type of epithelium covers the oral cavity and is important for protection?
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What is one primary function of epithelial tissue that assists in the movement of substances across its surface?
What is one primary function of epithelial tissue that assists in the movement of substances across its surface?
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Which gland is characterized by having both tubular and acinar secretory parts?
Which gland is characterized by having both tubular and acinar secretory parts?
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What happens to the superficial cell layer of transitional epithelium when the urinary bladder is full?
What happens to the superficial cell layer of transitional epithelium when the urinary bladder is full?
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Which type of epithelial tissue is specifically characterized by its columnar tall cells that often give a false appearance of stratification?
Which type of epithelial tissue is specifically characterized by its columnar tall cells that often give a false appearance of stratification?
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What is a characteristic feature of cells within glandular epithelia?
What is a characteristic feature of cells within glandular epithelia?
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Which type of epithelium is formed by multiple layers of cells and provides protection against abrasion?
Which type of epithelium is formed by multiple layers of cells and provides protection against abrasion?
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What type of secretion is typically produced by ceruminous glands?
What type of secretion is typically produced by ceruminous glands?
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What distinguishes simple columnar absorptive epithelium from other types of columnar epithelium?
What distinguishes simple columnar absorptive epithelium from other types of columnar epithelium?
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Which of the following glands releases secretions via exocytosis?
Which of the following glands releases secretions via exocytosis?
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Which type of epithelium would you primarily find lining the nasal cavity and respiratory tract due to its motile cilia?
Which type of epithelium would you primarily find lining the nasal cavity and respiratory tract due to its motile cilia?
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What characteristic of epithelial cells allows them to maintain their structural integrity?
What characteristic of epithelial cells allows them to maintain their structural integrity?
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Which of the following statements accurately describes transitional epithelium?
Which of the following statements accurately describes transitional epithelium?
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Which type of epithelial tissue typically has microvilli or cilia on its surface?
Which type of epithelial tissue typically has microvilli or cilia on its surface?
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Which specific type of secretion is produced by the parotid glands?
Which specific type of secretion is produced by the parotid glands?
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What type of glandular arrangement is described as 'ductless'?
What type of glandular arrangement is described as 'ductless'?
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Which anatomical locations are primarily covered by stratified squamous non-keratinized epithelium?
Which anatomical locations are primarily covered by stratified squamous non-keratinized epithelium?
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In which of the following locations would you find simple columnar ciliated epithelium?
In which of the following locations would you find simple columnar ciliated epithelium?
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Which feature is essential for the regeneration of epithelial tissue?
Which feature is essential for the regeneration of epithelial tissue?
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What is the secretion characteristic of sebaceous glands?
What is the secretion characteristic of sebaceous glands?
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Which structural adaptation allows transitional epithelium to accommodate varying degrees of stretching?
Which structural adaptation allows transitional epithelium to accommodate varying degrees of stretching?
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Which type of glandular epithelium is involved in secretion within glands?
Which type of glandular epithelium is involved in secretion within glands?
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In transitional epithelium, what is the composition that facilitates cell movement during fullness?
In transitional epithelium, what is the composition that facilitates cell movement during fullness?
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Which characteristic feature allows stratified squamous keratinized epithelium to provide a protective barrier?
Which characteristic feature allows stratified squamous keratinized epithelium to provide a protective barrier?
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What is a main characteristic of simple cuboidal epithelium?
What is a main characteristic of simple cuboidal epithelium?
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Which statement best describes the basal cells found in pseudostratified columnar epithelium?
Which statement best describes the basal cells found in pseudostratified columnar epithelium?
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What type of cells are primarily found in the superficial layer of transitional epithelium?
What type of cells are primarily found in the superficial layer of transitional epithelium?
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Which of the following locations is NOT primarily lined by transitional epithelium?
Which of the following locations is NOT primarily lined by transitional epithelium?
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What is a primary function of goblet cells found in certain types of epithelium?
What is a primary function of goblet cells found in certain types of epithelium?
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What occurs to transitional epithelium when the bladder is full?
What occurs to transitional epithelium when the bladder is full?
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Study Notes
Epithelial Tissue
- One of the four main types of tissue in the human body
- Covers external and internal surfaces of the body
- Forms most glands
- Highly cellular, with cells in close contact
- Polarized; apical and basal surfaces
- Rests on a basement membrane
- Avascular; nutrients and waste products transported by diffusion from underlying connective tissue
- Highly innervated
- Regenerative; high capacity for renewal
- Functions include protection, secretion, absorption, filtration, ion transportation, and creating slippery surfaces
Classifications of Epithelial Tissues
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Simple Epithelia: Single layer of cells
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Simple Squamous Epithelium: Flat, thin cells with centrally-located, flat nuclei
- Found in endothelium (lining of blood vessels) and mesothelium (lining of serous membranes)
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Simple Cuboidal Epithelium: Cube-shaped cells with centrally-located, rounded nuclei
- Found in renal tubules, thyroid follicles, and small ducts of exocrine glands
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Simple Columnar Epithelium: Tall, columnar cells with centrally-located, oval nuclei
- Found in the lining of the stomach (secretory) and small intestine (absorptive)
- Can have microvilli for increased absorption
- Can have cilia for movement of substances
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Pseudostratified Columnar Epithelium: Monolayer of cells with all resting on the basement membrane, but with some cells shorter than others, creating an illusion of stratification
- Found in the lining of the respiratory tract, large ducts of salivary glands, epididymis, and fallopian tubes
- May have cilia for movement of substances
- May have goblet cells for mucus secretion
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Simple Squamous Epithelium: Flat, thin cells with centrally-located, flat nuclei
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Stratified Epithelia: Multiple layers of cells
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Stratified Squamous Epithelium: Multiple cell layers with flat cells at the surface
- Non-keratinized: Found in moist areas like oral cavity, esophagus, anal canal, vagina, urethra
- Keratinized: Found in dry areas like the epidermis of skin
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Stratified Cuboidal (Transitional) Epithelium: Shape of superficial cells changes depending on stretch and pressure
- Found in the urinary bladder, pelvis of kidney, ureter, prostatic urethra
- Allows for expansion and contraction
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Stratified Columnar Epithelium: Multiple layers of cells with columnar cells at the surface
- Found in large ducts of salivary glands, recto-anal junction, and male urethra
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Stratified Squamous Epithelium: Multiple cell layers with flat cells at the surface
Glandular Epithelium
- Specialized for secretion
- Secretory granules store molecules to be secreted
- Divided into two types:
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Exocrine Glands: Have ducts; secretions carried to epithelial surface
- Examples: sweat glands, sebaceous glands, salivary glands
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Endocrine Glands: Ductless; secretions (hormones) released directly into the bloodstream
- Examples: pineal gland, pituitary gland, thyroid gland, suprarenal glands, testes, ovaries
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Exocrine Glands: Have ducts; secretions carried to epithelial surface
- Glandular epithelium can be unicellular or multicellular
- Examples of unicellular glands: goblet cells
- Examples of multicellular glands: salivary glands, pancreas
Types of Multicellular Glands
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Tubular: Tubular secretory part
- Examples: kidney, liver, testes, intestinal glands
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Acinar: Grape-like or acinar secretory part
- Examples: sebaceous glands
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Tubuloacinar: Possess both tubular and alveolar parts
- Examples: salivary glands, mammary glands, pancreas, prostate gland
Types of Glandular Secretions
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Mucous: Viscid, rich in carbohydrates
- Examples: goblet cells, minor salivary glands
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Serous: Watery, rich in enzymes
- Examples: parotid glands, pancreas
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Mixed: Combination of mucous and serous secretions
- Examples: submandibular and sublingual glands
- Fatty: Secreted from sebaceous glands and meibomian glands
- Waxy: Secreted from ceruminous glands of external ear canal
Modes of Exocrine Secretion
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Exocytosis: Secretion via membrane-bound vesicles
- Examples: sweat glands, salivary glands, mammary glands
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Holocrine Secretion: Cells lyse and release entire contents
- Examples: sebaceous glands, meibomian glands
Epithelium
- Epithelium tissues cover the outer surface of the body and inner surfaces of cavities.
- The cells are closely packed together with intercellular junctions.
- Epithelial tissue has a distinct apical and basal surface.
- The basal surface adheres to the basement membrane (BM).
- Epithelial cells can have modifications on their surface, such as microvilli or cilia.
- Epithelial tissue is avascular and nutrients are transported by diffusion from blood vessels in the connective tissue (CT).
- Epithelial tissue is highly innervated and has the ability to regenerate rapidly.
Functions of Epithelium
- Protection
- Secretion
- Absorption
- Filtration barrier
- Ion or gases transport
- Forms slippery surfaces
Types of Epithelial Tissue
- Covering and lining epithelium (external and internal surfaces)
- Glandular epithelium (secretory tissue in glands)
- Neuroepithelium
Classification of Epithelial Tissues
Simple Epithelium
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Simple Squamous Epithelium: Single layer of flat and thin cells with central, flat nuclei.
- Endothelium lines the heart, blood vessels, and lymph vessels.
- Mesothelium lines serous membranes around organs (pericardium, pleura, peritoneum).
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Simple Cuboidal Epithelium: Single layer of square shaped cells with central, rounded nuclei.
- Found in renal tubules, thyroid follicles, and small ducts of exocrine glands (e.g., salivary glands).
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Simple Columnar Epithelium: Single layer of columnar, tall cells with basal oval nuclei.
- Simple columnar epithelium can be secretory (e.g., stomach) or absorptive (e.g., small intestine - contains numerous microvilli).
- Simple columnar ciliated epithelium is found in bronchioles and fallopian tubes.
Pseudostratified Columnar Epithelium
- This type of epithelium is formed of a single layer of crowded cells where all cells rest on the BM.
- Some cells are short and fail to reach the surface, while the tall cells with oval nuclei reach the free surface.
- With the different heights of cells, and oval nuclei positioned at different levels, the appearance is that of a stratified epithelium.
- Pseudostratified columnar epithelium can be non-ciliated (e.g., large ducts of salivary glands) or ciliated with goblet cells (e.g., nasal cavity, trachea, bronchi).
- Pseudostratified columnar epithelium with non-motile cilia is found in the epididymis.
Stratified Epithelium
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Stratified Squamous Epithelium: Composed of multiple layers of cells, the basal layer rests on the BM.
- Classified according to the shape of the superficial cell layer.
- Stratified Squamous Non-Keratinized Epithelium: Upper layer of cells is formed of flat, non-dried, non-horny cells with central, rounded nuclei. Found in wet mucosas, such as the cornea, conjunctiva, oral cavity, esophagus, anal canal, urethra, and vagina.
- Stratified Squamous Keratinized Epithelium: Upper layer of cells is formed of flat, dried, horny, scaly cells filled with keratin. Found on the dry surface of the skin (epidermis).
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Stratified Cuboidal Epithelium (Transitional): Found in the urinary bladder, ureters, pelvis of the kidney, and prostatic urethra.
- The shape of the surface cells changes depending on the degree of stretch and pressure inside the urinary bladder.
- The cells rest on a thin BM, which can contract and expand.
- Formed from 5-8 layers, with columnar cells at the base, and large cubical cells with convex upper surface, central rounded nuclei (some binucleated) at the apex.
- The number of cell layers can change to 2 or 3 in a full bladder.
- The presence of mucous substance between the cells facilitates cell sliding during bladder distension.
- The superficial cell layer stretches and flattens temporarily.
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Stratified Columnar Epithelium: Composed of multiple cell layers with columnar cells at the surface.
- Found in large ducts of salivary glands, the recto-anal junction, and the membranous part of the male urethra.
Glandular Epithelium
- Glandular epithelia are found in glands and are specialized for secretion.
- Secretory products are stored in small membrane-bound vesicles called secretory granules.
- Two types of glands:
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Exocrine Glands: Have ducts and release their secretions into ducts.
- Examples: sweat glands, sebaceous glands, salivary glands.
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Endocrine Glands: Ductless, secrete hormones directly into the blood.
- Examples: pituitary gland, thyroid gland, adrenal gland, pancreas, testes, ovaries.
-
Exocrine Glands: Have ducts and release their secretions into ducts.
Types of Exocrine Glands
- Simple: Formed of a single cell (e.g., goblet cells) or numerous cells (e.g., salivary and pancreatic glands).
- Compound: Formed by a combination of types.
- Tubular: Secretory portion is tubular (e.g., kidney, liver, testes, intestinal glands).
- Acinar: Secretory portion is grape-like or acinar shapes (e.g., sebaceous glands).
- Tubulo-alveolar: Possess both tubular and alveolar structures (e.g., salivary glands, mammary glands, pancreas, prostate glands).
Mechanisms of Secretion
- Exocytosis: Cells secrete via exocytosis (e.g., sweat glands, salivary glands, mammary glands).
- Membrane-bound vesicles: Cells secrete via membrane-bound vesicles (e.g., sebaceous glands, meibomian glands).
- Cell lysis: The cell lysis and releases the entire contents of the cytoplasm and cell membrane during secretion (e.g., sebaceous glands, meibomian glands).
Summary of Secretion Types
- Viscid mucous poor in enzymes: Goblet cells and minor salivary glands.
- Watery solution rich in enzymes: Parotid glands and pancreas.
- Both types of secretions: Submandibular and sublingual glands.
- Watery secretion containing some enzymes and waste products: Sweat glands.
- Fatty secretion: Sebaceous and meibomian glands.
- Waxy secretion: Ceruminous glands of the external ear canal.
- Produce cells: Testis and ovary.
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