Skeletal System

• Comparative features of the vertebrae, ribs, and sterna:

  • Notochord is primitive axial skeleton, replaced by the vertebral column, unsegmented and composed of dense fibrous connective tissue
  • Vertebral column is segmented, arched rod flanked by axial musculature, suspends the trunk and protects the spinal cord
  • Parts of a typical vertebrae include centrum, arch, processes
  • Centrum serves to anchor and support the arches, may consist of one or two elements: intercentrum (cranial) and pleurocentrum (caudal)
• Arches:

  • Neural arches enclose a long vertebral canal occupied by the spinal cord, protect the neural tube
  • Hemal arches are inverted beneath the centra of the tail, house the caudal vessels, protect the blood vessels
• Processes or Apophyses:

  • Diapophyses (transverse processes) are articulating points for the ribs, serve as attachment for muscles
  • Zygapophyses are paired processes bearing articular surfaces by which neural arches articulate, with prezygapophyses in front and post zygapophyses in the rear
  • Parapophyses are lateral projections from the centra of a few tetrapods, serve as articulation site for bicipital rib
• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver

  
• Types of centra based on shape:

  • Amphicoelous: concave at both ends, limited motion in any direction, found in fishes, apoda, and some urodela
  • Opisthocoelous: convex in front and concave in back, permit motion in any direction, found in salamanders, parrots, and ungulates
  • Procoelous: concave in front and convex in back, permit motion in any direction, found in anurans and modern reptiles
  • Acoelous/Amphiplatyan: flat ended, can withstand compression and limit motion, found in mammals
  • Heterocoelous: saddle-shaped, allow vertical and lateral flexion but prevent rotation around the axis of the spine, found in birds
• Phylogeny of vertebra:

  • Rhachitomous present in earliest land vertebrates, centra retained geometric relationships but were more robust, articulating with one another and restricting the notochord
  • Stereospondylous have reduced or lost pleurocentra, intercentra become spool-shaped
  • Embolomerous have pleurocentra and intercentra become similar, giving each neural arch two spool-shaped centra
  • Gastrocentrous in amniotes and their relatives, pleurocentra enlarged and fused, intercentra reduced to small wedges or are lost
• Schaffer and Emerson's 1964 study on attachment:

  • Aim: identify stages of attachment / find a pattern in the development of an attachment between infants and parents
  • Participants: 60 babies from Glasgow
  • Procedure: analysed interactions between infants and carers
  • Findings: babies of parents/carers with 'sensitive responsiveness' were more likely to have formed an attachment
• Freud's superego represents internalized societal values and standards
• Mammals have varying numbers of sacral vertebrae:

  • Bears have a stout transverse process strong enough to bear the thrust of the pelvic girdles
  • Most mammals have 3 to 5 (ankylosed) sacral vertebrae, with exceptions like Perissodactyls having up to 8 and Edentates up to 13

  
• Synsacrum in mammals is the fusion of the last thoracic, all lumbars and sacral, and the first few caudals with the pelvic girdle, providing a rigid brace for the stance of birds
• Caudal vertebrae in mammals become progressively shorter and rudimentary towards the end, with the last segment being a small cylindrical centra
• Ribs in mammals articulate with vertebrae and extend into the body wall, formed intersegmentally by scleroblasts from two successive mesodermal somites like the centra
• Birds have thoracic ribs that are thin, flat, and broad with uncinate processes, and caudal ribs that are ankylosed to the synsacrum
• The sternum in mammals is composed of a series of bony segments or sternebrae, with the last sternebrae or the xiphisternum bearing a cartilaginous bony xiphoid process
• The skeleton shows broad outlines of vertebrate phylogeny and serves various functions like shape, protection, support, and muscle attachment for locomotion
• The skeleton can be categorized into exoskeleton (primitive trait) and endoskeleton (distinguishing characteristic of chordates)
• Mainly mineralized connective tissue deposited in collagen forms bone, cartilage, enameloids, and dentin in the skeletal system
• Ligaments connect bones to bones and hold them in place, while tendons connect muscles to bones
• Cartilage is a specialized connective tissue with chondrocytes dispersed in spaces in a matrix, surrounded by perichondrium
• Types of cartilage include hyaline, fibrous, elastic, and calcified cartilage, each with specific locations and functions
• Bone is a specialized connective tissue made up of calcified bone matrix, with different types of bone cells like osteogenic cells, osteoblasts, osteocytes, and osteoclasts
• Bones are classified based on shape, structure, origin, function, and position in the body, serving roles in support, protection, locomotion, hematopoiesis, and calcium storage
• Bones constantly remodel to accommodate organs they protect and respond to stress, with tendons connecting muscles to bones and ligaments connecting bones to bones
• Joints, classified as fibrous, cartilaginous, or synovial, play a vital role in connecting bones or cartilages in the skeletal system