review Flashcards
Functions of Bones
- Support – Provides structure and framework for the body.
- Protection – Shields vital organs (e.g., skull protects the brain).
- Leverage – Enables movement by acting as levers for muscles.
- Storage – Stores minerals (e.g., calcium, phosphorus).
- Blood Cell Formation – Produces blood cells in bone marrow.
Bone Composition
2nd hardest natural substance in the body.
Matrix: Contains cells and minerals.
Bone Cells:
1. Osteoblasts – Build new bone. (create)
2. Osteocytes – Mature bone cells surrounded by matrix. (maintain)
3. Osteoclasts – Break down and remodel bone. (dissolve)
Bone Structures
Types of Bone Tissue: Cancellous and Compact Bones
- Cancellous Bone (Spongy Bone)
- Light, porous, and contains bone
marrow.
- Spicules arranged to withstand stress
forces. - Compact Bone
- Dense, heavy, and strong.
- Found in the shafts of long bones and
outer layer of all bones.
- Organized into Haversian systems
(cylindrical structures).
Bone Structures
Bone Coverings: Periosteum and Endosteum
- Periosteum – Outer membrane; contains:
- Outer layer: Fibrous tissue.
- Inner layer: Osteoblasts (bone-forming
cells). - Endosteum – Lines the interior surfaces
of bones.
Blood Supply to Bones
Volkmann’s Canals, Haversian Canals, and Nutrient Foramina
- Volkmann’s Canals – Blood vessels running at right angles to Haversian canals, supply osteocytes
- Haversian Canals – Blood vessels, lymph vessels and nerves run lengthwise and center to a Haversian system, bring nutrients to osteocytes
- Nutrient Foramina – Large openings in long bones for blood vessels; may appear as fractures in X-rays. Carry blood in/out of bone marrow and bone
Bone Formation (Ossification)
Endochondral and Intramembranous
- Endochondral Bone Formation (Most bones)
- Cartilage template replaced by bone.
- Primary growth center: Diaphysis
(shaft).
- Secondary growth center: Epiphysis
(bone ends).
- Epiphyseal plates (growth plates)
ossify when mature. - Intramembranous Bone Formation
- Occurs only in certain skull bones.
- Bone develops from fibrous tissue
membranes.
Types of Bones
- Long Bones – Humerus, femur, radius,
tibia, metatarsals. - Flat Bones – Skull bones, scapula, ribs,
pelvis. - Short Bones – Carpals, tarsals.
- Irregular Bones – Vertebrae, some skull
bones.
Bone Marrow
Red and Yellow Bone Marrow
- Red Bone Marrow
- Produces blood cells (hematopoietic).
- Found in young animals.
- Yellow Bone Marrow
- Primarily adipose tissue (fat).
- Found in adults, but can revert to red
marrow if needed.
Divisions of the Skeleton
Axial, Appendicular, Visceral
- Axial Skeleton (Bones along the body’s
central axis)
- Skull, Hyoid bone, Vertebrae, Ribs,
Sternum - Appendicular Skeleton (Limb bones)
- Thoracic limbs – Scapula, humerus,
radius, ulna, carpus, metacarpus.
- Pelvic limbs – Pelvis, femur, tibia,
fibula, tarsus, metatarsus. - Visceral Skeleton (Bones within soft
tissues, organs (viscera))
- Os penis (in some male animals, dog).
- Os cordis (in the heart of cattle).
- Os rostri (in the snouts of pigs).
Humerus – Upper forelimb bone.
Radius & Ulna – Forearm bones.
Femur – Upper hindlimb bone.
Tibia & Fibula – Lower hindlimb bones.
Carpus – Wrist bones.
Tarsus – Ankle bones.
Metacarpus – Bones between the carpus
and phalanges (forelimb).
Metatarsus – Bones between the tarsus and
phalanges (hindlimb).
Skull – Protects the brain and supports the
structures of the face.
Mandible – Lower jawbone; The only
movable skull bone.
Pelvis – Supports the hind limbs and
connects the spine to the legs.
Rib – Flat bones form lateral walls of thorax
Forms the thoracic cage, protecting
the heart and lungs.
Scapula – Shoulder blade; connects the limb
to the body.
Patella – Kneecap; aids in movement of the
knee joint.
Phalanges – Toe and finger bones.
Skull
- Composed of many bones mostly
connected by immovable, fibrous joints
(sutures). - Mandible – The only movable skull bone.
Skull Bones
Bones of the Ear (Ossicles)
- Three small bones in the middle ear:
- Malleus (Hammer)
- Incus (Anvil)
- Stapes (Stirrup)
Bones of the Face
Internal Bones:
Turbinates (Nasal Conchae) – Four thin, scroll-like bones inside the nasal cavity that help filter and warm air.
Hyoid Bone (Hyoid Apparatus)
Supports the tongue and aids in swallowing.
Vertebrae
- Consist of a body, an arch, and processes.
- Intervertebral Disks – Made of fibrocartilage, separating vertebral bodies to act as cushions.
Ribs & Sternum
- Ribs – Flat bones that form the lateral walls of the
thorax. - Number of rib pairs = number of thoracic
vertebrae. - Dorsal heads of ribs articulate with
thoracic vertebrae. - Costal cartilage – Ventral portion of the ribs.
- Costochondral junction – Area where the cartilage
meets the bony rib.
Hormones & Bone Regulation
- Calcitonin (First Hormonal Mechanism) – released
with hypercalcemia, from thyroid gland, stimulates
osteoblasts, inhibits osteoclasts, blood calcium will
decrease bc its too high - Parathyroid Hormone (PTH) (Second Hormonal
Mechanism) – released with hypocalcemia, from
parathyroid gland, stimulates osteoclasts, inhibits
osteoblasts, and reduces urinary calcium excretion,
blood calcium will increase bc its too low - Growth Hormone – Stimulates bone growth during
development. - Sex Hormones (Estrogen & Testosterone)
– Help regulate bone growth and density.
Calcium Homeostasis:
First Hormonal Mechanism
Blood concentration of calcium is too high (hypercalcemia) –> calcitonin hormone is released by thyroid gland –> it inhibits the osteoclast activity and increases the osteoblast activity –> blood concentration of calcium decreases
Calcium Homeostasis:
Second Hormonal Mechanism
Blood concentration of calcium is too low (hypocalcemia) –> Parathyroid hormone is released by parathyroid gland –> it increases the osteoclast activity and inhibits the osteoblasts activity. It also reduces the urinary calcium excretion –> blood concentration of calcium increases
