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Lecture 1.2 Connective tissue; Cartilage and Bone

Jennifer Olson・42 minutes read

Various types of tissues in the human body, such as connective, epithelial, muscle, and nervous tissues, serve different functions and have distinct structures. Connective tissue includes components like cells, protein fibers, and ground substance, with different types like loose and dense connective tissues offering support and strength to the body's structures.

Insights

  • Different types of tissues in the human body have distinct structures and functions, with connective tissue being the most diverse and widespread, supporting, protecting, and binding various structures together through cells, protein fibers, and ground substance.
  • Bone tissue comprises compact and spongy bone, with osteocytes housed in lacunae and connected through canaliculi, allowing for communication and nutrient exchange, while bone formation and repair processes involve osteoblasts, osteocytes, and osteoclasts to maintain bone integrity and strength.

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Recent questions

  • What are the main tissue classes in the human body?

    Connective, epithelial, muscle, and nervous tissues.

  • What are the functions of connective tissue?

    Support, protection, binding, storage, and transportation.

  • What are the types of bone tissue in the human body?

    Compact bone and spongy bone.

  • How does bone growth occur in long bones?

    Appositional growth at outer surfaces and endochondral ossification.

  • What is the process of fracture repair in bones?

    Blood clot formation, collagen fiber production, osteoblast activity, remodeling, and healing.

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Summary

00:00

Understanding Human Body Tissues: Structure and Function

  • Tissues in the human body consist of cells and extracellular products serving common functions, with varying consistencies from fluid to solid based on their roles.
  • Tissues' structures are closely linked to their functions, with support tissues being rigid, protective tissues being multi-layered, and diffusion facilitators having few layers.
  • The human body comprises four main tissue classes: connective, epithelial, muscle, and nervous tissues, each differing in cell specialization and extracellular matrices.
  • Connective tissue, the most diverse and widespread type, supports, protects, and binds structures together, encompassing bones, cartilage, tendons, ligaments, body fat, and blood.
  • Connective tissue contains cells, protein fibers, and ground substance, serving functions like physical protection, support, binding, storage, and transportation.
  • Post-birth connective tissue is categorized into connective tissue proper, supporting connective tissue, and fluid connective tissue, all originating from mesenchymal cells.
  • Fluid connective tissue includes blood and lymph, with blood containing red and white blood cells, platelets, dissolved proteins, and plasma, while lymph lacks formed elements.
  • Supporting connective tissue comprises cartilage and bone, while connective tissue proper is further divided into loose and dense connective tissues, each with distinct characteristics.
  • Loose connective tissue, like areolar, adipose, and reticular tissues, acts as the body's packing material, while dense connective tissue, including regular, irregular, and elastic types, offers strength and support.
  • Resident cells in connective tissue proper, like fibroblasts, mesenchymal cells, and macrophages, produce protein fibers and ground substance, with collagen, elastic, and reticular fibers strengthening and supporting tissues.

15:16

Types and Functions of Connective Tissue

  • Connective tissue is divided into six types, including loose connective tissue and dense connective tissue.
  • Supporting connective tissue consists of cartilage and bone, with cartilage having three forms: hyaline, fibrocartilage, and elastic.
  • Bone tissue includes compact bone and spongy bone, with bones categorized into long, short, flat, and irregular shapes.
  • Cartilage is a semi-rigid connective tissue that provides support, a gliding surface at articulations, and a model for bone formation.
  • Cartilage cells, or chondrocytes, are found in lacunae and produce a chemical that prevents blood vessel formation.
  • Hyaline cartilage is the most common type, found in the nose, trachea, and fetal skeleton, while fibrocartilage is durable and used for shock absorption.
  • Elastic cartilage is flexible and resilient, found in structures like the external ear and epiglottis.
  • Bone structure includes the diaphysis, epiphysis, and metaphysis, with articular cartilage reducing friction in joints.
  • Bone cells include osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts, involved in bone formation and resorption.
  • Compact bone forms the walls of bones, while spongy bone has a more open network and is found in the epiphysis and medullary cavity.

30:58

Bone Structure and Growth: A Summary

  • Osteocytes in bone are housed in lacunae between concentric lamellae, with extensions of osteocytes traveling through canaliculi, tiny interconnecting channels within the bone.
  • Canaliculi allow osteocytes to connect, communicate, and pass nutrients and wastes to and from blood vessels within the central canal.
  • Compact bone micrographs show concentric lamellae surrounding the central canal with lacunae where osteocytes are located.
  • Spongy bone differs from compact bone in its lattice-like trabeculae structure, providing strength despite being lighter.
  • Osteocytes in spongy bone are housed in lacunae between parallel lamellae, unlike compact bone's concentric lamellae.
  • Ossification is the formation of bone connective tissue, starting in the embryo and continuing through childhood and adolescence.
  • Long bone growth involves appositional growth at outer surfaces, with stem cells differentiating into osteoblasts to add bone matrix.
  • Interstitial growth in long bones occurs through endochondral ossification, where hyaline cartilage is replaced by bone.
  • Bone density peaks in the 20s and decreases with age due to reduced collagen production and calcium loss, leading to weaker bones.
  • Fracture repair involves blood clot formation, collagen fiber production, and osteoblast activity to replace bone, with eventual remodeling and healing.

45:56

Growth Plate Fractures: Types and Prognosis

  • The Psalter Harris classification system, established in 1863, is widely used to categorize growth plate fractures. Type 1 fractures involve a transverse fracture through the growth plate without affecting the bone, while type 2 fractures occur above the growth plate, partially crossing it and extending through the metaphysis. Both type 1 and type 2 fractures have a positive prognosis if properly stabilized. In contrast, type 3 fractures pass through the growth plate and down to the bone's articular surface, while type 4 fractures traverse the metaphysis, growth plate, and epiphysis, leading to a poorer prognosis due to potential physio bar formation.
  • Type 5 fractures, although rare, result from crushing injuries that severely damage the growth plate without displacing it. This type of fracture has the worst prognosis, halting growth at the affected end. An example illustrates a case where a distal femur fracture caused significant growth discrepancy between the legs, with the affected leg being several inches shorter due to stunted growth.
  • Ian's case involved a fracture close to the growth plate but not passing through it. Immobilized in a Spica cast, Ian's hip joint was stabilized for proper healing. Despite the challenges posed by the cast, Ian's recovery was successful after approximately 7 weeks, leading to a fully functional leg, albeit with restrictions to prevent risky activities like jumping on furniture.
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