Biology 264: Bone Structure and the Axial Skeleton Flashcards

A Comprehensive vocabulary set covering calcium homeostasis, bone histology, gross anatomy of long bones, and the major features of the axial skeleton based on lab lecture slides.

Hypocalcemia

A condition characterized by low blood calcium levels which triggers the release of parathyroid hormone (PTH).

Hypercalcemia

A condition characterized by excess blood calcium levels which triggers the release of calcitonin from the thyroid gland.

Parathyroid Hormone (PTH)

A hormone secreted by the parathyroid glands during hypocalcemia that activates osteoclasts to release calcium from bone into the blood.

Calcitonin

A hormone secreted by the thyroid gland during blood calcium excess that increases osteoblast activity for bone deposition and reduces osteoclast activity.

Osteoblast

A bone-building cell that traps itself in the matrix to become an osteocyte; its activity reduces blood calcium levels and increases bone density.

Osteoclast

A bone-dissolving cell (resorption) from a different lineage that uses lysosomes to break down bone and release calcium into the blood.

$$Ca_{10}(PO_4)_6(OH)_2$$

The chemical formula for Hydroxyapatite, which makes up approximately 85% of the inorganic dry weight of bone.

Osteoid

The organic part of the bone matrix, representing roughly 1/3 of bone dry weight, which is a protein similar to collagen.

Osteon

The structural unit of compact (cortical) bone, characterized by lamellae arranged around a central (osteonic) canal.

Trabeculae

The irregular latticework of lamellae found exclusively in spongy (cancellous or trabecular) bone; it lacks a central canal.

Lacunae

Small cavities within the bone matrix that house mature bone cells called osteocytes.

Canaliculi

Tiny channels that connect lacunae, allowing for communication and nutrient transfer between osteocytes.

Periosteum

An external layer of connective tissue that covers the compact bone exterior and forms joint capsules.

Endosteum

A thin layer that covers the internal spongy bone and the medullary cavity inside.

Diaphysis

The shaft of a long bone that contains the medullary cavity.

Epiphysis

The ends of a long bone, typically filled with spongy bone and supporting red bone marrow.

Articular Cartilage

A type of hyaline cartilage that covers bone surfaces inside a joint capsule.

Epiphyseal Line

A layer of compact bone in adult long bones that represents the remains of the childhood hyaline cartilage growth plate.

Sesamoid Bone

A category of bone shape found within tendons, such as the patella.

Axial Skeleton

The division of the skeleton consisting of the skull, vertebral column, thoracic cage, hyoid bone, and inner ear ossicles.

Suture

An immobile, fibrous joint found between the flat bones of the skull, such as the coronal, squamous, lambdoid, and sagittal sutures.

Foramen Magnum

The large opening in the occipital bone that allows the medulla oblongata or spinal cord to pass through.

Sella Turcica

A saddle-like depression in the sphenoid bone where the pituitary gland is located.

Fontanel

The 'soft spots' or membrane-filled spaces in a fetal skull, such as the anterior (frontal) or posterior (occipital) fontanels.

Atlas (C1)

The first cervical vertebra that supports the skull.

Axis (C2)

The second cervical vertebra, characterized by the dens (odontoid process) which allows for rotation of the head.

Transverse Foramina

Unique holes found only in the 7 cervical vertebrae that house blood vessels.

Intervertebral Foramina

Openings formed when vertebrae stack together, through which spinal nerves exit the spinal cord.

Kyphosis

An abnormal curvature of the vertebral column often associated with the thoracic region (hunchback).

Lordosis

An abnormal anterior curvature of the lumbar vertebral column (swayback).

Scoliosis

An abnormal lateral curvature of the vertebral column.

True Ribs

Ribs 1-7, which have their own individual costal (hyaline) cartilage connections to the sternum.

False Ribs

Ribs 8-12, which do not have a direct individual connection to the sternum.

Floating Ribs

Ribs 11-12, a subset of false ribs that have no attachment to the sternum at all.

Xiphoid Process

The small, inferior-most part of the sternum.