{"id":688,"date":"2021-01-20T04:32:31","date_gmt":"2021-01-20T04:32:31","guid":{"rendered":"https:\/\/pressbooks.publishdot.com\/anatomyphysiology\/chapter\/11-7-fibrous-joints\/"},"modified":"2021-12-07T09:38:38","modified_gmt":"2021-12-07T09:38:38","slug":"11-7-fibrous-joints","status":"publish","type":"chapter","link":"https:\/\/pressbooks.publishdot.com\/anatomyphysiology\/chapter\/11-7-fibrous-joints\/","title":{"raw":"11.7 Fibrous Joints","rendered":"11.7 Fibrous Joints"},"content":{"raw":"
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Learning Objectives<\/strong><\/p>\n\n<\/header>\n

\n\nBy the end of this section, you will be able to:\n
    \n \t
  • Describe the structural features of fibrous joints<\/li>\n \t
  • Distinguish between a suture, syndesmosis and gomphosis<\/li>\n \t
  • Give an example of each type of fibrous joint<\/li>\n<\/ul>\n<\/div>\n<\/div>\nAt a fibrous joint, the adjacent bones are directly connected to each other by fibrous connective tissue, and thus the bones do not have a joint cavity between them (Figure 11.7.1). The gap between the bones may be narrow or wide. There are three types of fibrous joints. A suture is the narrow fibrous joint found between most bones of the skull. At a syndesmosis joint<\/strong>, the bones are more widely separated but are held together by a narrow band of fibrous connective tissue called a ligament<\/strong> or a wide sheet of connective tissue called an interosseous membrane<\/strong>. This type of fibrous joint is found between the shaft regions of the long bones in the forearm and in the leg. Lastly, a gomphosis is the narrow fibrous joint between the roots of a tooth and the bony socket in the jaw into which the tooth fits.\n\n[caption id=\"attachment_687\" align=\"aligncenter\" width=\"624\"]\"Diagram Figure 11.7.1. Fibrous joints.<\/strong> Fibrous joints form strong connections between bones. (a) Sutures join most bones of the skull. (b) An interosseous membrane forms a syndesmosis between the radius and ulna bones of the forearm. (c) A gomphosis is a specialised fibrous joint that anchors a tooth to its socket in the jaw.[\/caption]\n

    Suture<\/h2>\nAll the bones of the skull, except for the mandible, are joined to each other by a fibrous joint called a suture<\/strong>. The fibrous connective tissue found at a suture (\u201cto bind or sew\u201d) strongly unites the adjacent skull bones and thus helps to protect the brain and form the face. In adults, the skull bones are closely apposed and fibrous connective tissue fills the narrow gap between the bones. The suture is frequently convoluted, forming a tight union that prevents most movement between the bones. (See Figure 11.7.1a). Thus, skull sutures are functionally classified as a synarthrosis, although some sutures may allow for slight movements between the cranial bones.\n\nIn newborns and infants, the areas of connective tissue between the bones are much wider, especially in those areas on the top and sides of the skull that will become the sagittal, coronal, squamous, and lambdoid sutures. These broad areas of connective tissue are called fontanelles<\/strong> (Figure 11.7.2). During birth, the fontanelles provide flexibility to the skull, allowing the bones to push closer together or to overlap slightly, thus aiding movement of the infant\u2019s head through the birth canal. After birth, these expanded regions of connective tissue allow for rapid growth of the skull and enlargement of the brain. The fontanelles decrease in width during the first year after birth as the skull bones enlarge. When the connective tissue between the adjacent bones is reduced to a narrow layer, these fibrous joints are now called sutures. At some sutures, the connective tissue will ossify and be converted into bone, causing the adjacent bones to fuse to each other. This fusion between bones is called a synostosis<\/strong> (\u201cjoined by bone\u201d). Examples of synostosis fusions between cranial bones are found both early and late in life. At the time of birth, the frontal and maxillary bones consist of right and left halves joined together by sutures, which disappear by the eighth year as the halves fuse together to form a single bone. Late in life, the sagittal, coronal, and lambdoid sutures of the skull will begin to ossify and fuse, causing the suture line to gradually disappear.\n\n[caption id=\"attachment_687\" align=\"aligncenter\" width=\"624\"]\"Diagram Figure 11.7.2. The newborn skull.<\/strong> The fontanelles of a newborn\u2019s skull are broad areas of fibrous connective tissue that form fibrous joints between the bones of the skull.[\/caption]\n

    Syndesmosis<\/h2>\nA syndesmosis<\/strong> (\u201cfastened with a band\u201d) is a type of fibrous joint in which two parallel bones are united to each other by fibrous connective tissue. The gap between the bones may be narrow, with the bones joined by ligaments, or the gap may be wide and filled in by a broad sheet of connective tissue called an interosseous membrane.\n\nIn the forearm, the wide gap between the shaft portions of the radius and ulna bones are strongly united by an interosseous membrane (see Figure 11.7.1b). Similarly, in the leg, the shafts of the tibia and fibula are also united by an interosseous membrane. In addition, at the distal tibiofibular joint, the articulating surfaces of the bones lack cartilage and the narrow gap between the bones is anchored by fibrous connective tissue and ligaments on both the anterior and posterior aspects of the joint. Together, the interosseous membrane and these ligaments form the tibiofibular syndesmosis.\n\nThe syndesmoses found in the forearm and leg serve to unite parallel bones and prevent their separation. However, a syndesmosis does not prevent all movement between the bones, and thus this type of fibrous joint is functionally classified as an amphiarthrosis. In the leg, the syndesmosis between the tibia and fibula strongly unites the bones, allows for little movement, and firmly locks the talus bone in place between the tibia and fibula at the ankle joint. This provides strength and stability to the leg and ankle, which are important during weight bearing. In the forearm, the interosseous membrane is flexible enough to allow for rotation of the radius bone during forearm movements. Thus, in contrast to the stability provided by the tibiofibular syndesmosis, the flexibility of the antebrachial interosseous membrane allows for the much greater mobility of the forearm.\n\nThe interosseous membranes of the leg and forearm also provide areas for muscle attachment. Damage to a syndesmotic joint, which usually results from a fracture of the bone with an accompanying tear of the interosseous membrane, will produce pain, loss of stability of the bones, and may damage the muscles attached to the interosseous membrane. If the fracture site is not properly immobilised with a cast or splint, contractile activity by these muscles can cause improper alignment of the broken bones during healing.\n

    Gomphosis<\/h2>\nA gomphosis<\/strong> (\u201cfastened with bolts\u201d) is the specialised fibrous joint that anchors the root of a tooth into its bony socket within the maxillary bone (upper jaw) or mandible bone (lower jaw) of the skull. A gomphosis is also known as a peg-and-socket joint. Spanning between the bony walls of the socket and the root of the tooth are numerous short bands of dense connective tissue, each of which is called a periodontal ligament<\/strong> (see Figure 11.7.1c). Due to the immobility of a gomphosis, this type of joint is functionally classified as a synarthrosis.\n
    \n

    Section Review<\/strong><\/p>\n\n<\/header>\n

    \n\nFibrous joints are where adjacent bones are strongly united by fibrous connective tissue. The gap filled by connective tissue may be narrow or wide. The three types of fibrous joints are sutures, gomphoses, and syndesmoses. A suture is the narrow fibrous joint that unites most bones of the skull. At a gomphosis, the root of a tooth is anchored across a narrow gap by periodontal ligaments to the walls of its socket in the bony jaw. A syndesmosis is the type of fibrous joint found between parallel bones. The gap between the bones may be wide and filled with a fibrous interosseous membrane, or it may narrow with ligaments spanning between the bones. Syndesmoses are found between the bones of the forearm (radius and ulna) and the leg (tibia and fibula). Fibrous joints strongly unite adjacent bones and thus serve to provide protection for internal organs, strength to body regions, or weight-bearing stability.\n\n<\/div>\n<\/div>\n
    \n

    Review Questions<\/strong><\/p>\n\n<\/header>\n

    \n\n[h5p id=\"360\"]\n\n<\/div>\n<\/div>\n
    \n

    Critical Thinking Questions<\/strong><\/p>\n\n<\/header>\n

    \n\n[h5p id=\"361\"]\n\n[h5p id=\"362\"]\n\n<\/div>\n<\/div>\nClick the drop down below to review the terms learned from this chapter.\n\n[h5p id=\"363\"]","rendered":"
    \n
    \n

    Learning Objectives<\/strong><\/p>\n<\/header>\n

    \n

    By the end of this section, you will be able to:<\/p>\n

      \n
    • Describe the structural features of fibrous joints<\/li>\n
    • Distinguish between a suture, syndesmosis and gomphosis<\/li>\n
    • Give an example of each type of fibrous joint<\/li>\n<\/ul>\n<\/div>\n<\/div>\n

      At a fibrous joint, the adjacent bones are directly connected to each other by fibrous connective tissue, and thus the bones do not have a joint cavity between them (Figure 11.7.1). The gap between the bones may be narrow or wide. There are three types of fibrous joints. A suture is the narrow fibrous joint found between most bones of the skull. At a syndesmosis joint<\/strong>, the bones are more widely separated but are held together by a narrow band of fibrous connective tissue called a ligament<\/strong> or a wide sheet of connective tissue called an interosseous membrane<\/strong>. This type of fibrous joint is found between the shaft regions of the long bones in the forearm and in the leg. Lastly, a gomphosis is the narrow fibrous joint between the roots of a tooth and the bony socket in the jaw into which the tooth fits.<\/p>\n

      \"Diagram
      Figure 11.7.1. Fibrous joints.<\/strong> Fibrous joints form strong connections between bones. (a) Sutures join most bones of the skull. (b) An interosseous membrane forms a syndesmosis between the radius and ulna bones of the forearm. (c) A gomphosis is a specialised fibrous joint that anchors a tooth to its socket in the jaw.<\/figcaption><\/figure>\n

      Suture<\/h2>\n

      All the bones of the skull, except for the mandible, are joined to each other by a fibrous joint called a suture<\/strong>. The fibrous connective tissue found at a suture (\u201cto bind or sew\u201d) strongly unites the adjacent skull bones and thus helps to protect the brain and form the face. In adults, the skull bones are closely apposed and fibrous connective tissue fills the narrow gap between the bones. The suture is frequently convoluted, forming a tight union that prevents most movement between the bones. (See Figure 11.7.1a). Thus, skull sutures are functionally classified as a synarthrosis, although some sutures may allow for slight movements between the cranial bones.<\/p>\n

      In newborns and infants, the areas of connective tissue between the bones are much wider, especially in those areas on the top and sides of the skull that will become the sagittal, coronal, squamous, and lambdoid sutures. These broad areas of connective tissue are called fontanelles<\/strong> (Figure 11.7.2). During birth, the fontanelles provide flexibility to the skull, allowing the bones to push closer together or to overlap slightly, thus aiding movement of the infant\u2019s head through the birth canal. After birth, these expanded regions of connective tissue allow for rapid growth of the skull and enlargement of the brain. The fontanelles decrease in width during the first year after birth as the skull bones enlarge. When the connective tissue between the adjacent bones is reduced to a narrow layer, these fibrous joints are now called sutures. At some sutures, the connective tissue will ossify and be converted into bone, causing the adjacent bones to fuse to each other. This fusion between bones is called a synostosis<\/strong> (\u201cjoined by bone\u201d). Examples of synostosis fusions between cranial bones are found both early and late in life. At the time of birth, the frontal and maxillary bones consist of right and left halves joined together by sutures, which disappear by the eighth year as the halves fuse together to form a single bone. Late in life, the sagittal, coronal, and lambdoid sutures of the skull will begin to ossify and fuse, causing the suture line to gradually disappear.<\/p>\n

      \"Diagram
      Figure 11.7.2. The newborn skull.<\/strong> The fontanelles of a newborn\u2019s skull are broad areas of fibrous connective tissue that form fibrous joints between the bones of the skull.<\/figcaption><\/figure>\n

      Syndesmosis<\/h2>\n

      A syndesmosis<\/strong> (\u201cfastened with a band\u201d) is a type of fibrous joint in which two parallel bones are united to each other by fibrous connective tissue. The gap between the bones may be narrow, with the bones joined by ligaments, or the gap may be wide and filled in by a broad sheet of connective tissue called an interosseous membrane.<\/p>\n

      In the forearm, the wide gap between the shaft portions of the radius and ulna bones are strongly united by an interosseous membrane (see Figure 11.7.1b). Similarly, in the leg, the shafts of the tibia and fibula are also united by an interosseous membrane. In addition, at the distal tibiofibular joint, the articulating surfaces of the bones lack cartilage and the narrow gap between the bones is anchored by fibrous connective tissue and ligaments on both the anterior and posterior aspects of the joint. Together, the interosseous membrane and these ligaments form the tibiofibular syndesmosis.<\/p>\n

      The syndesmoses found in the forearm and leg serve to unite parallel bones and prevent their separation. However, a syndesmosis does not prevent all movement between the bones, and thus this type of fibrous joint is functionally classified as an amphiarthrosis. In the leg, the syndesmosis between the tibia and fibula strongly unites the bones, allows for little movement, and firmly locks the talus bone in place between the tibia and fibula at the ankle joint. This provides strength and stability to the leg and ankle, which are important during weight bearing. In the forearm, the interosseous membrane is flexible enough to allow for rotation of the radius bone during forearm movements. Thus, in contrast to the stability provided by the tibiofibular syndesmosis, the flexibility of the antebrachial interosseous membrane allows for the much greater mobility of the forearm.<\/p>\n

      The interosseous membranes of the leg and forearm also provide areas for muscle attachment. Damage to a syndesmotic joint, which usually results from a fracture of the bone with an accompanying tear of the interosseous membrane, will produce pain, loss of stability of the bones, and may damage the muscles attached to the interosseous membrane. If the fracture site is not properly immobilised with a cast or splint, contractile activity by these muscles can cause improper alignment of the broken bones during healing.<\/p>\n

      Gomphosis<\/h2>\n

      A gomphosis<\/strong> (\u201cfastened with bolts\u201d) is the specialised fibrous joint that anchors the root of a tooth into its bony socket within the maxillary bone (upper jaw) or mandible bone (lower jaw) of the skull. A gomphosis is also known as a peg-and-socket joint. Spanning between the bony walls of the socket and the root of the tooth are numerous short bands of dense connective tissue, each of which is called a periodontal ligament<\/strong> (see Figure 11.7.1c). Due to the immobility of a gomphosis, this type of joint is functionally classified as a synarthrosis.<\/p>\n

      \n
      \n

      Section Review<\/strong><\/p>\n<\/header>\n

      \n

      Fibrous joints are where adjacent bones are strongly united by fibrous connective tissue. The gap filled by connective tissue may be narrow or wide. The three types of fibrous joints are sutures, gomphoses, and syndesmoses. A suture is the narrow fibrous joint that unites most bones of the skull. At a gomphosis, the root of a tooth is anchored across a narrow gap by periodontal ligaments to the walls of its socket in the bony jaw. A syndesmosis is the type of fibrous joint found between parallel bones. The gap between the bones may be wide and filled with a fibrous interosseous membrane, or it may narrow with ligaments spanning between the bones. Syndesmoses are found between the bones of the forearm (radius and ulna) and the leg (tibia and fibula). Fibrous joints strongly unite adjacent bones and thus serve to provide protection for internal organs, strength to body regions, or weight-bearing stability.<\/p>\n<\/div>\n<\/div>\n

      \n
      \n

      Review Questions<\/strong><\/p>\n<\/header>\n

      \n
      \n