The skeletal system is made up of 206 bones divided into the axial skeleton (80 bones) and appendicular skeleton (126 bones). It provides structure, stores minerals, protects organs, allows movement, and produces blood cells. The endocrine system regulates hormones like growth hormone that control bone growth and maintenance by stimulating osteoblast activity and mineralization. Hypopituitarism is a condition where the pituitary gland fails to produce enough hormones like growth hormone, which can lead to decreased bone mass and osteoporosis.

1. THE SKELETAL SYSTEM
Milestone 3
Alexandra Perkins

2. Table of Contents
Anatomical Location
and Features
Key Physiological
Features
Histology
CONNECTION:
Endocrine and
Skeletal System
Hypopituitarism
Growth Hormone
Insufficiency

3. Anatomical Location and Features
This system is made up of 206 individual bones (Marieb, 2015)
• Two major divisions:
• axial skeleton
• appendicular skeleton
The skeleton makes up about 30-40% of an adult’s body mass (Taylor, 2020)
Bones are composed of water (50%), collagen protein, and solid crystals of
calcium carbonate and calcium phosphate (50%) (Taylor, 2020)

4. Anatomical Location and Features
• Skull
• Hyoid
• Auditory ossicles
• Ribs
• Sternum
• Vertebral column
•The axial skeleton includes (80 bones):
• Upper limbs
• Lower limbs
• Pelvic girdle
• Pectoral (shoulder) girdle
The appendicular skeleton includes (126 bones):
(Taylor, 2020)

5. Axial Skeleton: highlighted in blue
Appendicular Skeleton: highlighted in gold
(Marieb, 2015)

6. Histology
Spongy Bone
• Trabeculae
enclosed marrow
and blood
vessels and
canaliculi (for
communication)
Compact
Bone
• Osteons are the
functional units
(encased in
lamellae)
Periosteum
• Outermost layer
of bone involved
in repairing
fractures
Endosteum
• Production of
osteoprogenitor
cells and
osteoclasts
(Crumbie, 2020)
Osteoclasts
• Remove bone
during growth
and healing
Osteoblasts
• Build bone by
facilitating
mineralization of
osteoid matrix
(Crumbie, 2020)
Osteocytes
• Osteoblasts that
have become
trapped in the
bone matrix and
communicate
with other
osteoblasts and
osteocytes.
(Crumbie, 2020)

7. KEY
PHYSIOLOGICAL
FEATURES

8. Providing support
• Provides structure for the entire body
• Individual bones provide the framework for the attachment of soft tissue and organs
Stores minerals and lipids
• The calcium salts located in the bones are a vital mineral that maintain normal levels of calcium and phosphate ions in bodily fluids
• Bones also store energy in fat (lipids) (Biga et al., 2020)
Hematopoieses
• The marrow of the bones produce red blood cells, white blood cells and other blood elements
• Produced in the Medullary Cavity (Taylor, 2020)
Protect body organs
• Vital organs and soft tissue are surrounded and protected by the skeleton.
• The rib cage protects the heart and lungs
Provide leverage and movement
• Bones allow the individual to change the magnitude and direction of forces generate by muscles (Taylor, 2020)

9. Diagram of bone growth and remodeling (Marieb, 2015).

10. THE SKELETAL AND
ENDOCRINE SYSTEM
CONNECTION:
Endocrine and Skeletal
System

11. The endocrine system regulates hormones important for bone growth.
• Poor bone density
• Directly affects osteoblasts and osteoblasts through the Growth Hormone (GH) and Insulin-like Growth Factor (IGF-1) (Chang et al., 2018).
Dysregulation of hormones can result in:
The endocrine system is responsible for controlling bone growth, maintaining bone once it is formed,
and remodeling bone (Biga et al., 2020)
• Increases the length of bones
The pituitary gland (endocrine system) secretes GH which triggers chondrocyte proliferation in
epiphyseal plates (Biga et al., 2020)
• Enhances mineralization
• Stimulates osteoblastic activity
• Improves bone density
The Growth Hormone also increases calcium retention in bonesm (Kim, 2015)

12. Other hormones controlled by the endocrine system that affect the skeletal system (Biga et al., 2020; Chang et al., 2018)
• Stimulates bone growth
• Promotes synthesis of bone matrix
•Thyroxine
• Promote osteoblastic activity
• Promotes synthesis of bone matrix
• Responsible for adolescent growth spurts
• Promotes conversion of epiphyseal plat to epiphyseal line
Sex Hormones
• Stimulates absorption of calcium and phosphate from the digestive tract
Calcitriol
• Stimulates osteoclast proliferation and resorption of bone by osteoclasts
• Promotes reabsorption of calcium via kidney tubules
• Indirectly increases calcium absorption by small intestine
Parathyroid Hormone
• Inhibits osteoclast activity
• Simulates calcium uptake by bones
Calcitonin

13. A chronic endocrine illness
resulting in hormone
deficiencies, specifically
hormones GH and
adrenocorticotropic hormone
(ACTH) (Chang et al., 2018)
"Hypopituitarism is defined as
the total or partial loss of
anterior and posterior pituitary
gland function that is caused by
pituitary or hypothalamic
disorders" (Kim, 2015).
Affects regulation of bone
growth and development in
osteoblasts and osteoclasts.
A prevalence rate of 300 to 455
patients per million; a rare
disease (Taylor, 2020).
30% to 70% of patients with
brain injury exhibit symptoms
of diminished hormone
secretion from their pituitary
gland (Kim, 2015)
Hypopituitarism

14. Deficiencies in the Growth
Hormone and ACTH result in:
Decreased bone
mass
May result in
osteoporosis
Acromegaly
Overproduction of GH
during adulthood resulting in
increased size of bones
including hands, feet, and
face (Biga et al., 2020).
Caused by
pituitary
adenoma
Occurs after
epiphyseal plate
closure
Adult Growth
Hormone
Deficiency
(AGHD)
Not enough GH
Caused by
intrinsic pituitary
dysfunction
Causes
prolonged stress
and peripheral
insensitivity to
GH
Hypopituitarism
(Chang et al., 2018; Kim, 2015)

15. References
Biga, L. M., Dawson, S., Harwell, A., Hopkins, R., Kaufmann, J., LeMaster, M., Matern, P., Morrison-Graham, K., Quick, D., & Runyeon, J. (2020).
Exercise, Nutrition, Hormones, and Bone Tissue. Oregon State University. https://open.oregonstate.education/aandp/chapter/6-6-exercise-nutrition-
hormones-and-bone-tissue/#:~:text=The%20endocrine%20system%20produces%20and,is%20formed%2C%20and%20remodeling%20it.
Chang, R. G., Bazmi, K., & Beaufort, A. (2018). Endocrine abnormalities affecting the musculoskeletal system. https://now.aapmr.org/endocrine-
abnormalities-affecting-the-musculoskeletal-system/
Crumbie, L. (2020). Bone histology. https://www.kenhub.com/en/library/anatomy/histology-of-bone
Kim S. Y. (2015). Diagnosis and Treatment of Hypopituitarism. Endocrinology and metabolism (Seoul, Korea), 30(4), 443–
455. https://doi.org/10.3803/EnM.2015.30.4.443
Marieb, E. N. (2015). Essentials of human anatomy (10th ed.). Glenview, IL: Pearson Education
Taylor, T. (2020). Skeletal system. Innerbody Research. https://www.innerbody.com/image/skelfov.html