Cytology · MU Pleven

Topic 32. Connective tissues - connective tissues with dense intercellular substance.

Covers bone as a dense connective tissue, outlining its functions, matrix composition (organic and inorganic parts, with hydroxyapatite), and calcification. It describes the four bone cell types with their origins and roles, then osteogenesis through intramembranous and endochondral ossification, growth zones of the epiphyseal plate, nutritional factors, and fracture repair and remodelling.

Inside: 7 sections · 3 labelled pictures · 43 flashcards · 11 min

Topic 32 of 59 in the MU Pleven syllabus for Cytology (Medicine, Year 1). The free AceMed note covers it in 7 sections, about 1,608 words (11 min of reading), with 43 flashcards.

In this note

  1. TOPIC 32- connective tissues with dense intercellular substance (Bones)
  2. Bone cell types
  3. Calcification
  4. Osteogenesis – Bone Formation
  5. Bone Growth:
  6. Factors affecting bone growth
  7. Bone remodelling and repair

TOPIC 32- connective tissues with dense intercellular substance (Bones)

  • Bones are one of the hardest tissues of the human body
  • Richly vascularised
  • Main constituent of adult skeleton
  • Reservoir of calcium (99%), phosphate and other ions
  • Good regeneration capacity

Main functions:

  1. 1. Protection of vital organs in the cranial and thoracic cavities
  2. 2. Forms a system of levers to enhance the body movements
  3. 3. The bone is the primary structural framework for the support and protection of our body and organs and it provides a reserve for Calcium (99%) and Phosphate minerals. The minerals can be released with control to maintain constant concentrations in the body fluids. It also aids body movements and produces blood cells.

Bone is the main constituent of the adult skeleton and is a specialised connective tissue which has dense intercellular substance.

Difference between cartilage and bone is that the ECM of bone contains Calcium which calcifies making the bones hard, its highly vascularised and can repair itself well.

The outer surface of the bone is covered by the periosteum and the central cavity is lined by the endosteum.

Mature bone matrix normally is approximately 35% organic and 65% inorganic material. The organic material consists of collagen, proteoglycans and glycoproteins (osteonectin – adhesive). The inorganic material consists of a calcium phosphate crystal called hydroxyapatite. There are also matrix vesicles with alkaline phosphatase in the matrix, released by osteoblasts.

Substances are unable to diffuse through the calcified bone matrix, the exchanges between osteocytes and blood capillaries depend on communication through the very thin, cylindrical spaces of the canaliculi. Bone canaliculi are microscopic canals between the lacunae of ossified bone.

The ground substance of the bone is rich in proteoglycans associated with collagen fibres. Cells which can be found in the bones are the osteoprogenitor cells, osteoblasts and osteoclasts.

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