Exam 3 Study Packet Hormones and the Skeletal System

Flashcards based on the key concepts from the Exam 3 Study Packet regarding hormones, bone cells, and muscle contraction.

Growth hormone

Most important hormone in stimulating epiphyseal plate activity during childhood.

Parathyroid hormone (PTH)

Hormone that helps regulate blood calcium levels by stimulating bone resorption.

Estrogen and Testosterone

Promote bone growth and stimulate the closure of epiphyseal plates during puberty.

Osteocalcin

Hormone secreted by bones that regulates insulin secretion and glucose metabolism.

Calcitonin

Hormone that decreases blood calcium levels by inhibiting osteoclast activity.

Wolf’s Law

States that bones grow or remodel in response to demands placed on them.

Osteoblast

Bone cell that is responsible for secreting an unmineralized bone matrix (osteoid).

Osteoclast

Bone cell whose primary function is bone resorption.

Osteocyte

Bone cell that maintains the bone matrix and communicates with osteoblasts and osteoclasts.

Canaliculi

Micro-channels through which osteocytes communicate about bone stress.

Epiphyseal plate closure

Occurs around 18 years of age in females and 21 years of age in males.

Osteoporosis

Disease characterized by decreased bone mass where resorption exceeds bone deposit.

Rickets

A disorder characterized by abnormal bone length and joint deformities due to vitamin D deficiency.

Muscle contraction

The process that leads to muscle tension and movement.

Isometric contraction

A contraction where the muscle does not shorten, but tension increases.

Isotonic contraction

A contraction where the muscle shortens because tension exceeds the load.

Rigor mortis

A state of constant muscle contraction caused by increased calcium levels and lack of ATP.

T/F: Growth hormone is responsible for stimulating bone resorption when blood calcium levels are low.

False – Growth hormone stimulates bone growth, not bone resorption.

T/F: Estrogen and testosterone promote bone growth but also induce the closure of the epiphyseal plate at the end of puberty

True

T/F: Parathyroid hormone decreases the activity of osteoclasts to lower calcium levels in the blood.

False – Parathyroid hormone increases osteoclast activity to release calcium into the blood.

T/F: Calcitonin is a hormone that increases blood calcium levels by stimulating osteoblast activity.

False – Calcitonin decreases blood calcium levels by inhibiting osteoclast activity.

Stress is usually _____, so bones tend to bend.

off center

Bending _______ one side, and ______ the other side.

compresses, stretches

T/F:  Bones in a sedentary person are thinner than in an active person.

True because mechanical stress (from activity) promotes bone density and strength, and inactivity leads to weaker bones, consistent with Wolf’s Law.

Where are osteocytes located within bone tissue?

lacunae

What is the function of osteogenic cells in bone tissue?

form new bone cells

What happens to osteoclasts after they complete the bone resorption process?

undergo apoptosis

The _____ zone of the epiphyseal plate is where the cartilage is relatively inactive and serves as a reserve for new cells.

resting

In the ______ zone, chondrocytes (cartilage cells) rapidly divide, pushing the epiphysis away from the diaphysis and lengthening the bone.

proliferation

The ____ zone is characterized by older chondrocytes closer to the diaphysis, where cartilage lacunae enlarge and erode.

hypertrophic

 In the ____ zone, cartilage matrix calcifies, causing chondrocytes to die and deteriorate.

calcification

The ____ zone is where chondrocyte deterioration leaves spicules of calcified cartilage, which are later replaced with bone.

ossification

T/F: The epiphyseal plate closes and bone lengthening ceases once the epiphyseal cartilage has been replaced by bone.

True

Results in soft, weak bones due to inadequate calcium salts being deposited. 

Osteomalacia

Characterized by excessive and disorganized bone deposit and resorption, often affecting the spine, pelvis, femur, and skull.

Paget’s Disease

What happens to the bones in individuals with rickets?

The bone ends become enlarged and abnormally long

Order of endochondral ossification:

•  Bone collar forms around the diaphysis of the hyaline cartilage model.

•  Central cartilage in the diaphysis calcifies, and cavities develop.

•  The periosteal bud invades the cavities, leading to the formation of spongy bone.

•  Diaphysis elongates, and a medullary cavity forms.

•  Epiphyses Ossify.

A joint cavity is filled with

synovial fluid

Surfaces of the bones are covered with _____ cartilage.

articular

A fibrous _____ surrounds the joint and helps hold it together.

capsule

The joint cavity is enclosed by a _______ membrane that secretes synovial fluid.

synovial

Limited movement

Amphiartrhoses

Freely movable

Diarthroses

No movement

Synarthroses

What makes synovial joints different from fibrous and cartilaginous joints?

They have a fluid-filled space between the bones

Which type of joint is held together by dense fibrous connective tissue and typically allows little to no movement?

Fibrous joints

Which type of joint is made of bones joined by cartilage and allows only limited movement?

Cartilaginous joints

Blood vessels break and a clot (hematoma) forms; the area swells and becomes painful.

Hematoma formation

New blood vessels grow in, debris is cleared, and soft tissue (fibers and cartilage) bridges the break.

Fibrocartilaginous callus formation

Spongy bone replaces the soft callus, forming a hard, bony callus over several weeks.

bony callus formation

 The bone is reshaped and strengthened over time to match its original form and handle stress.

bone remodeling