Bone Tissue and Physiology: Overview of Bones

• Unit 6 is concerning bone tissue and physiology
• Unit 7 covers the axial skeleton

Overview of Bones

• Bones provide protection, mineral storage, red blood cell formation, fat storage, movement, and support
• The adult human skeleton is comprised of 206 bones

Osseous Tissue Types

• Compact bone is deep to the periosteum and composed of osteons
• Spongy bone is deep to the compact bone and composed of trabeculae, and houses red bone marrow
• The hard, calcified matrix contains collagen fibers, with osteocytes lying in lacunae
• Bone is very vascularized

Bone Shapes

• There are five major bone shapes
• Long bones, such as the humerus
• Short bones, such as the tarsals
• Flat bones, such as the scapula
• Irregular bones, such as the vertebrae
• Sesamoid bones, such as the patella

Long Bones Anatomy

• Articular cartilage and red bone marrow are some structures of long bones
• Proximal and distal epiphyses differ on the humerus, ulna, radius, femur, and tibia

Compact Bone Features

• "Osteons" are compact bone's functional subunits
• Lamellae make up mineralized ECM, provide strength, and can be circumferential, concentric, and interstitial
• Central (Haversian) canals run down the osteon centers and provide a canal for vessels/nerves
• Lacunae serve as the "home" to osteocytes
• Canaliculi are connections between lacunae
• Perforating (Volkmann's) canals are perpendicular canals
• Sharpey's Fibers anchor the periosteum with collagen fibers

Spongy Bone Features

• Spongy bone is arranged in trabeculae
• The trabeculae resists compression

Skeletal Overview

• The axial skeleton forms central supporting axis of the body and is comprised of the skull, vertebrae, sternum, ribs, sacrum, and hyoid.
• Accessory structures include skeletal cartilages, tendons, and ligaments
• There are three types of skeletal cartilages: hyaline cartilage, fibrocartilage, and elastic cartilage
• Tendons attach muscle to bone and are made of dense regular connective tissue
• Ligaments attach bone to bone and are made of dense regular connective tissue

Bone Markings: Depressions

• Facet: shallow/concave surface where bones articulate
• Fovea: shallow pit
• Fossa: indentation into which another structure fits
• Groove: long indentation

Bone Markings: Openings

• Canal: tunnel
• Fissure: narrow slit
• Foramen: hole

Bone Markings: Projections

• Condyle: rounded end (articulation)
• Crest: ridge
• Tubercle and tuberosity: small, rounded
• Epicondyle: proximal to a condyle
• Process: prominent bony projection
• Spine: sharp process
• Head: round projection from epiphysis
• Protuberance: Outgrowth from a bone
• Trochanter: Large projection (only in femur)
• Line: long narrow ridge

Axial Skeleton

• The axial skeleton (skull) contains cranial and facial bones

Cranial Bones

• There are eight cranial bones
• The cranial bones are the frontal bone, parietal bone (x2), temporal bone (x2), sphenoid, ethmoid, and occipital
• The sphenoid bone articulates with the temporal, parietal, and frontal bones, forming a "weak spot" called the temple

Facial Bones

• The nasal bones (x2), lacrimal bones (x2), palatine bone (x2), zygomatic bone (x2), inferior nasal concha (x2) and maxilla (x2) are facial bones.
• Additional facial bones are the mandible, and vomer

Hyoid Bone

• The hyoid bone does not articulate with any other bone
• It is suspended by ligaments and muscle
• It allows movement of the tongue and swallowing

Vertebral Column

• There are five vertebral groups
• Seven cervical vertebrae are in the neck
• Twelve thoracic vertebrae are in the chest
• Five lumbar vertebrae are in the lower back
• Five fused sacral vertebrae are at the spine base
• Four fused coccygeal vertebrae
• Variations in the number of lumbar and sacral vertebrae occur in 1 in 20 people

Thoracic Cage

• Identifiable structures are the ribs
• Identifiable structures are the number of ribs of each type