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Lobe (anatomy)
Lobe (anatomy)
Lobe (anatomy)
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Lobes
Visceral surface of the liver showing the four lobes
Identifiers
TA98A13.1.02.002
FMA45728
Anatomical terminology

In anatomy, a lobe is a clear anatomical division or extension[1] of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to the much smaller lobule, which is a clear division only visible under the microscope.[2]

Interlobar ducts connect lobes and interlobular ducts connect lobules.

Examples of lobes

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Examples of lobules

[edit]
Lobules of the mammary glands.

References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Lobe (anatomy)

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In anatomy, a lobe refers to a distinct, rounded subdivision of an organ that is often separated from adjacent parts by fissures, grooves (sulci), , or other boundaries, allowing for specialized functional within the organ. This term, derived from the Greek "lobos" meaning a small rounded projection, is commonly applied to glandular and solid organs such as the , liver, lungs, , and breasts. The brain's cerebral hemispheres are classically divided into four main lobes per side: the , responsible for executive functions like and ; the , involved in sensory processing and spatial awareness; the , associated with auditory processing, memory, and language; and the , dedicated to visual interpretation. In the liver, the organ is externally divided into a larger right lobe and a smaller left lobe by the , with further functional segmentation into eight sectors based on vascular and biliary anatomy to support , , and protein synthesis. The lungs exhibit asymmetry in lobation, with the right lung comprising three lobes (superior, middle, and inferior) separated by horizontal and oblique fissures, while the left lung has two lobes (superior and inferior) due to the cardiac notch, facilitating efficient across a combined surface area of approximately 70–80 square meters. These lobar divisions aid in surgical planning and disease localization, such as in lobectomies for cancer.

General Concepts

Definition

In anatomy, a lobe is defined as a principal subdivision of an organ or , typically a rounded or projecting portion that is visible on gross examination and separated from adjacent parts by natural boundaries such as fissures, sulci, or septa. This demarcation emphasizes both structural and functional independence, allowing lobes to operate as semi-autonomous units within the organ while contributing to its overall . Lobes are commonly delineated by specific anatomical features, including invaginations of the visceral pleura in the lungs, interlobar fissures in the liver, or patterns of sulci and gyri in the , which provide clear planes of separation observable during or . These boundaries ensure that lobes maintain distinct vascular, neural, and lymphatic supplies, supporting their role in localized processes. The term "lobe" derives from the Latin lobus, meaning a rounded projection or pod, rooted in usage for similar anatomical features like the or liver protrusions; it entered modern anatomical nomenclature through 16th-century texts, notably Andreas Vesalius's De Humani Corporis Fabrica (1543), where it described organ divisions such as the two lobes of the human liver, correcting earlier misconceptions of five lobes. While anatomy serves as the standard reference, lobe configurations vary across ; for instance, quadrupedal mammals like dogs and cats typically exhibit more pulmonary lobes (four in the right and two in the left) compared to the configuration of three in the right and two in the left, reflecting adaptations to posture and respiratory demands. Lobules represent smaller subdivisions within these lobes, further refining organizational hierarchy.

Anatomical Characteristics

Lobes in anatomical structures are primarily composed of , the functional tissue responsible for the organ's primary activities, which is typically enclosed by a thin fibrous capsule or partitioned by septa originating from the capsule. These septa penetrate the parenchyma, creating distinct boundaries that define individual lobes and facilitate structural organization. In many organs, this arrangement supports compartmentalization, allowing for efficient internal architecture. The vascular supply to lobes is organized through dedicated lobar arteries that branch from the primary arterial supply of the organ, paralleled by corresponding lobar veins that converge into the main venous drainage. This segmental vascular pattern ensures targeted to each lobe, promoting parallel blood flow and optimizing resource distribution across the organ. Innervation follows a similar lobar distribution, with autonomic extending along vascular pathways to innervate specific regions, enabling coordinated yet localized neural control. Functionally, lobes serve as modular units within organs, permitting independent growth, repair mechanisms, and containment of pathological processes, which enhances overall organ resilience and efficiency. For instance, this allows damage or disease in one lobe to be isolated without compromising the entire organ, as exemplified by conditions like where infection remains confined to a single lobe. Embryologically, lobar boundaries arise during organ development through mesenchymal septation, where partitions divide the primordium, or epithelial folding, which shapes tissue protrusions into distinct lobes. These processes, involving interactions between epithelial and mesenchymal layers, establish the foundational architecture during .

Lobes in Major Organs

Cerebral Lobes

The cerebral lobes are the principal divisions of the , each delineated by prominent sulci and gyri that adapt the general lobar concept of compartmentalized tissue to the folded architecture of neural . The four major lobes—frontal, parietal, temporal, and occipital—are visible on the brain's surface, while the insular lobe lies deeper within the . These divisions facilitate specialized processing of sensory, motor, and cognitive information, with boundaries primarily defined by the (separating frontal and parietal lobes), the (marking the superior limit of the ), and the (distinguishing parietal from occipital). Additionally, the forms a functional ring encircling the , comprising structures like the cingulate and parahippocampal gyri, which integrate , , and . The , occupying the anterior portion of each anterior to the and superior to the lateral fissure, governs , voluntary , and aspects of speech production. Its resides in the (), while in the (Brodmann areas 44 and 45, typically left-hemisphere dominant) supports language articulation. The , posterior to the and anterior to the , integrates somatosensory information via the (Brodmann areas 3, 1, and 2). The , inferior to the lateral fissure, processes auditory input in the () and contributes to memory formation, with (Brodmann area 22, left-dominant) enabling language comprehension. The , posterior to the , specializes in visual processing through the primary visual cortex (Brodmann area 17). Deep within the lateral fissure, the insular lobe handles gustatory sensations, autonomic regulation, and multimodal sensory integration. These lobes underpin higher and exhibit hemispheric specialization, where the left hemisphere often dominates and logical tasks, while the right supports spatial and creative functions. Damage to specific lobes yields distinct clinical s; for instance, can precipitate frontal lobe , characterized by personality alterations, impulsivity, , and impaired social judgment due to prefrontal cortex disruption. Temporal lobe pathology frequently manifests as , involving focal seizures with auras like or fear, automatisms, and potential memory deficits, often originating from mesial structures and refractory to medication in up to 75% of cases. Such lobar impairments highlight the brain's modular organization in supporting integrated neural operations.

Hepatic Lobes

The liver is anatomically divided into four lobes: the right lobe, left lobe, caudate lobe, and quadrate lobe. The right lobe is the largest, comprising approximately 60% of the total liver mass, while the left lobe accounts for about 40%, with the caudate and quadrate lobes being smaller accessory structures. These lobes are separated by key ligaments and structures: the divides the right and left lobes along the anterior surface, the demarcates the caudate lobe posteriorly between the and the left lobe, and the defines the quadrate lobe on the inferior surface anterior to the portal triad. Functionally, the hepatic lobes contribute to the liver's metabolic roles, including , production, and processing, though the right lobe's greater size provides a dominant contribution to overall and synthesis capacity. The left lobe, being smaller and better oxygenated in certain contexts, supports glucose storage and metabolism. Vascular supply to the lobes occurs via the dual hepatic circulation: the delivers 70-75% of blood (-rich from the ), and the provides 25-30% (oxygenated blood), with lobar branches distributing to each lobe before forming portal triads within functional units. Venous drainage follows (right, middle, left) that converge into the , with the right hepatic vein handling the largest volume at about 40%. In surgical and imaging contexts, the hepatic lobes guide procedures like , where right hepatectomy removes the right lobe to treat tumors while preserving left lobe function, relying on preoperative volumetry to ensure adequate remnant liver mass. Imaging via CT or MRI visualizes lobes and their Couinaud segments—eight functional sub-lobes defined by bifurcations and hepatic vein planes (e.g., segments V-VIII in the right lobe, I-IV in the left and caudate)—enabling precise assessment for resection planning. Embryologically, the hepatic lobes develop from ventral and dorsal endodermal buds arising from the during the third week of , which fuse and expand into the , leading to asymmetric lobation through rotation and remodeling of fetal venous structures like the . This process establishes the right lobe's dominance and the caudate lobe's unique position by the eighth week.

Pulmonary Lobes

The lungs are divided into lobes by fissures, with the right lung consisting of three lobes—upper, middle, and lower—separated by a horizontal fissure between the upper and middle lobes and an oblique fissure between the middle and lower lobes. In contrast, the left lung has two lobes—upper and lower—separated solely by an oblique fissure, a configuration influenced by the cardiac notch that accommodates the heart and reduces space for a middle lobe. Each lobe is enveloped by visceral pleura, which forms a smooth covering and contributes to the pleural cavity's function in reducing friction during respiration. The bronchial tree branches into lobar bronchi that supply each lobe specifically, with the right main bronchus dividing into upper, middle, and lower lobar bronchi, while the left divides into upper and lower lobar bronchi. Lymphatic drainage from the lobes occurs via peribronchial and hilar (lobar) nodes, which collect fluid and immune cells before routing to mediastinal nodes. Functionally, the lobes contribute to efficient , with ventilation and varying by position due to : the upper lobes (apical regions) exhibit a higher ventilation-perfusion (V/Q) ratio of approximately 2.1, promoting effective oxygenation despite lower blood flow, while the lower lobes (basal regions) have a lower V/Q ratio of about 0.3, optimizing elimination amid greater . This gravity-dependent adaptation enhances overall respiratory efficiency in the upright posture, as the bases receive about 50% more ventilation than the apices due to greater alveolar compliance. Clinically, lobar anatomy is critical in conditions like , where obstruction can cause isolated lobe collapse, impairing local . Infections such as may preferentially affect certain lobes, exemplified by right middle lobe syndrome, a recurrent atelectasis and infection of the right middle lobe due to anatomical narrowing and poor collateral ventilation. In thoracic , lobectomy involves removing an entire affected lobe, often for malignancies, preserving remaining function while addressing localized disease.

Lobules and Subdivisions

Definition of Lobules

In , a lobule is defined as a small lobe or a subdivision of a larger lobe within an organ, serving as a basic structural and functional unit. These subunits are typically polygonal or polyhedral in shape, often hexagonal, and arranged in a tessellated that tiles the tissue efficiently. Lobules are commonly separated by thin septa, which provide structural support and house vascular, lymphatic, or ductal elements. Lobules function as the building blocks of larger lobes, with multiple lobules aggregating to form the parent structure; this allows for modular function and repair within organs. In terms of scale, lobules range from microscopic (visible only under a ) to mesoscopic (discernible with the ), contrasting with the macroscopic size of lobes. Histologically, each lobule often features a central axis, such as a , duct, or , around which parenchymal cells radiate; for instance, in hepatic lobules, a central drains , while portal triads (containing , , and ) lie at the periphery. In glandular tissues, lobules exhibit acinar organization, where clusters of secretory acini converge on intralobular ducts. The term "lobule" applies variably across contexts, denoting gross anatomical divisions in organs like the lungs, where secondary pulmonary lobules are bounded by interlobular septa, and microscopic compartments in structures such as the testes, divided by fibrous septa into lobules containing seminiferous tubules.

Examples of Lobules

In the liver, hepatic lobules serve as the primary functional units, characterized by a classical hexagonal arrangement of plates radiating from a central , with portal triads—consisting of a branch, hepatic artery branch, and —located at each of the six vertices. This structure facilitates the flow of nutrient-rich blood from the portal triads through sinusoids toward the central , while produced by s flows in the opposite direction via canaliculi to the triads, enabling efficient metabolic processing and detoxification. In pathological conditions such as , disrupts this lobular architecture, leading to regenerative nodules and impaired vascular flow. In the lungs, secondary pulmonary lobules represent discrete structural units measuring approximately 1 to 2.5 cm in diameter, bounded by septa and containing multiple acini (terminal respiratory units) along with centrilobular bronchioles, pulmonary arteries, and veins. These lobules are particularly visible on (HRCT) scans, where their septa and internal components aid in diagnosing localized diseases affecting ventilation and , such as interstitial lung disorders. Renal lobules consist of clusters of nephrons in the cortex, separated by medullary rays that extend from the renal pyramids, forming conical units that integrate and urine concentration processes. In the mammary gland, each contains 15 to 20 lobules, which are glandular clusters of alveoli responsible for milk production during , each draining into a that converges at the . Testicular lobules, numbering around 250 per testis, are pyramidal compartments divided by septa from the tunica albuginea, each enclosing 1 to 4 coiled seminiferous tubules where occurs. Across organs, lobules vary significantly in size and density—ranging from the compact, numerous testicular units (approximately 250 per organ) to the larger, fewer pulmonary secondary lobules (1-2 cm each)—reflecting adaptations to specific physiological demands, such as high-throughput in kidneys or localized in lungs, which in turn influence patterns like nodular regeneration in cirrhotic livers.

References

  1. https://www.rxlist.com/lobe/definition.htm
  2. https://www.ncbi.nlm.nih.gov/books/NBK538496/
  3. https://www.ncbi.nlm.nih.gov/books/NBK500014/
  4. https://www.ncbi.nlm.nih.gov/books/NBK470197/
  5. https://www.ncbi.nlm.nih.gov/books/NBK534789/
  6. https://www.ncbi.nlm.nih.gov/books/NBK553123/
  7. https://medical-dictionary.thefreedictionary.com/lobe
  8. https://www.sciencedirect.com/topics/medicine-and-dentistry/lobe-anatomy
  9. https://www.etymonline.com/word/lobe
  10. https://circulatingnow.nlm.nih.gov/2014/04/09/andreas-vesalius-and-de-fabrica/
  11. https://pmc.ncbi.nlm.nih.gov/articles/PMC4589993/
  12. https://www.kenhub.com/en/library/anatomy/the-lung
  13. https://radiopaedia.org/articles/lung?lang=us
  14. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2435.13486
  15. https://radiopaedia.org/articles/lobar-pneumonia?lang=us
  16. https://www.ncbi.nlm.nih.gov/books/NBK549789/
  17. https://www.ncbi.nlm.nih.gov/books/NBK538491/
  18. https://www.ncbi.nlm.nih.gov/books/NBK570606/
  19. https://www.ncbi.nlm.nih.gov/books/NBK532981/
  20. https://www.ncbi.nlm.nih.gov/books/NBK549852/
  21. https://journals.indianapolis.iu.edu/index.php/IMPRS/article/view/22699/22102
  22. https://www.ncbi.nlm.nih.gov/books/NBK535438/
  23. https://pmc.ncbi.nlm.nih.gov/articles/PMC1779658/
  24. https://pmc.ncbi.nlm.nih.gov/articles/PMC4038911/
  25. https://embryology.oit.duke.edu/GI/GI.html
  26. https://www.ncbi.nlm.nih.gov/books/NBK532863/
  27. https://www.ncbi.nlm.nih.gov/books/NBK539907/
  28. https://www.ncbi.nlm.nih.gov/books/NBK547657/
  29. https://www.tabers.com/tabersonline/view/Tabers-Dictionary/734638/all/lobule
  30. https://www.sciencedirect.com/topics/medicine-and-dentistry/liver-lobule
  31. https://www.kenhub.com/en/library/anatomy/liver-histology
  32. https://histology.siu.edu/intro/glands.htm
  33. https://radiopaedia.org/articles/secondary-pulmonary-lobule?lang=us
  34. https://www.elsevier.com/resources/anatomy/urogenital-system/male-genital-system/septa-testis-medial-part-right/25007
  35. https://histology.siu.edu/erg/liver.htm
  36. https://www.ncbi.nlm.nih.gov/books/NBK482419/
  37. https://pubmed.ncbi.nlm.nih.gov/16543587/
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC8165947/
  39. https://pmc.ncbi.nlm.nih.gov/articles/PMC7271189/
  40. https://www.ncbi.nlm.nih.gov/books/NBK547666/
  41. https://training.seer.cancer.gov/anatomy/reproductive/male/testes.html
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