07 Skeletal System

Skeletal system

Support, protection, activity/movement

making blood + storage

Hemopoiesis

blood cell production

Osteoclast

breaks down bone

Osteoblast

builds bone

Osteocyte

maintains the bone matrix, bone cell

detect mechanical stress

Osteoprogenitor

starting cell, can become osteoblasts

Osteon

basic unit of compact bone

Central canal

blood vessels, nerves

Concentric lamellae

rings of bone around the central canal

Lacuna

little space where osteocyte lives

Canaliculi

tiny channels connecting lacunae, communication and transport

Volkmann/Perforating canals

connect central canals btwn osteons

Trabeculae

rods/plates forming the meshwork

bone marrow fills the spaces

Avascular

no blood vessels

Hyaline cartilage

flexible, resilient, high in water, good shock absorber, highly compressible, avascular, contains no nerves

chondroblasts

produce cartilage matrix

chondrocytes

mature cartilage cells

maintain cartilage matrix

live in the lacunae

Ossification

formation/development of bone

osteogenesis - begins during embryonic development and continues through childhood/adolescence

Intramembranous ossification

membrane development

Endochondral ossification

Cartilage development

interstitial

growth in bone length

in the cartilage (epiphyseal plate)

Appositional

increases bone diameter/thickness

occurs at the periosteum

Epiphyseal plate

allows the bone to grow in length

Epiphyseal line

bone done growing

stronger bones

more weight-bearing

bone loss

Less mechanical stress

Growth hormone

Anterior pituitary

stimulate the liver to produce Somatomedin

Thyroid hormone

thyroid gland - helps regulate normal activity at the epiphyseal plates and affects bone cell metabolism

Sex hormones

Estrogen + testosterone

Glucocorticoids

adrenal cortex

high amount = bad for bone

Calcium

Muscle contraction, exocytosis, heart activity, blood clotting

PTH

raises blood calcium

low blood calcium > PTH released

increases osteoclast activity

Calcitonin

lower blood calcium

high blood calcium > calcitonin released

Aging

bones become weaker

osteoblast protein synthesis decreases

Osteopenia

mild/general bone loss with aging

less serious

35-40

Osteoblast activity decreases while osteoclast activity remains at previous levels

Osteoporosis

reduced bone mass that compromises normal function

more serious - porous bone

Fractures

Simple = 2 - 3 months to heal

compound = take longer

Calcitriol

Calcium get absorbed into blood