The Skeletal System

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Questions and Answers

What type of cartilage is initially present in endochondral formation?

Elastic cartilage

Fibrocartilage

Chondroid cartilage

Hyaline cartilage (correct)

What is the primary function of cells that erode bone?

To enable the body to extract calcium from bones

To produce calcium hydroxyapatite

To remodel bone that is not needed (correct)

To connect to other bone cells via gap junctions

What is the role of osteoblasts in endochondral formation?

They form the medullary cavity in the diaphysis (correct)

They stimulate the activity of osteoclasts

They promote the absorption of calcium from the intestines

They break down bone tissue

What is the function of parathyroid hormone (PTH) in bone physiology?

It increases the activity of osteoclasts and releases calcium into blood circulation Signup and view all the answers

What is the main component of bone that provides flexibility?

Collagen Signup and view all the answers

What is the purpose of bone lining cells?

To cover inactive bone surfaces Signup and view all the answers

What is the effect of calcitriol on bone physiology?

It stimulates the activity of osteoclasts and promotes calcium absorption from the intestines Signup and view all the answers

What is the term for the process of bone change throughout an animal's life?

Bone remodeling Signup and view all the answers

What is the function of calcitonin in bone physiology?

It reduces the activity of osteoclasts and promotes calcium deposition in bones Signup and view all the answers

What is the characteristic of intramembranous formation?

It occurs only in the skull bones Signup and view all the answers

What type of bone is evident in the adult skeleton?

Cancellous bone Signup and view all the answers

What is the function of gap junctions in bone lining cells?

To connect to other bone cells Signup and view all the answers

What is the purpose of the epiphyseal plate in long bone growth?

It produces new cartilage cells on the diaphysis side Signup and view all the answers

What is the final outcome of bone healing?

Complete restoration of the original bone structure Signup and view all the answers

What is the primary component of bone that provides strength?

Calcium hydroxyapatite Signup and view all the answers

What is the function of cells that extract calcium from bones?

To enable the body to extract calcium from bones for blood Signup and view all the answers

What is the role of calcitriol in calcium absorption?

It promotes calcium absorption from the intestines Signup and view all the answers

What is the term for the process of bone formation and resorption?

Bone remodeling Signup and view all the answers

What is unique about the roots of the cheek teeth in the Hystricomorpha suborder?

They grow continuously through life Signup and view all the answers

What is the primary function of the beak shape variation in birds?

To adapt to different food sources Signup and view all the answers

What is the term for the joint present between the maxillary beak and skull in birds?

Kinetic hinge joint Signup and view all the answers

What is unique about the teeth of Chelonians?

They are similar to those of birds Signup and view all the answers

What is the function of the vertebral discs in the spinal column?

To act as shock absorbers Signup and view all the answers

What is a characteristic of the incisors of Myomorph rodents?

They are continuously growing Signup and view all the answers

What is a unique feature of the teeth of snakes?

They are curved and pointed Signup and view all the answers

What is the term for the gap between the incisors and cheek teeth in rodents?

Diastema Signup and view all the answers

What is a characteristic of the teeth of Lizards?

They are peg-like and in four rows Signup and view all the answers

What is the primary function of the annulus fibrosus in the vertebral column?

Providing a surface for muscle attachment Signup and view all the answers

Which cervical vertebra is responsible for a nodding movement?

C1 – atlas Signup and view all the answers

How many thoracic vertebrae are present in dogs and cats?

13 Signup and view all the answers

What is the name of the joint formed by the atlas and the axis?

Atlanto-axial joint Signup and view all the answers

What is the characteristic of the spinous processes in the thoracic region?

They are tall and spinous Signup and view all the answers

What is the function of the lateral part of the thoracic vertebrae?

It connects to the ribs Signup and view all the answers

How many vertebrae are present in the lumbar region of dogs and cats?

7 Signup and view all the answers

What is the characteristic of the sacral region?

It is composed of 3 fused vertebrae Signup and view all the answers

What is the joint that connects the sacrum to the pelvis?

Sacroiliac joint Signup and view all the answers

Which of the following bones is responsible for supporting the shoulder joint and shell in chelonians?

Coracoid bone Signup and view all the answers

What is the term for the ventral joint that connects the two halves of the pelvis?

Pelvic symphysis Signup and view all the answers

Which of the following bones is the largest sesamoid bone in the body?

Patella Signup and view all the answers

What is the term for the hole on either side of the pelvic symphysis that makes the pelvis lighter?

Obturator foramina Signup and view all the answers

Which of the following bones is fused with the proximal row of tarsal bones in birds?

Tibia Signup and view all the answers

What is the term for the intertarsal joint in birds that is equivalent to the hock joint in other animals?

Suffrago joint Signup and view all the answers

Which of the following bones is rotated in chelonians?

Ilium Signup and view all the answers

What is the term for the separate bone that forms the structure of the hip joint in rabbits?

Os acetabuli Signup and view all the answers

Which of the following bones is fused with the distal row of tarsal bones in birds?

Metatarsal bone Signup and view all the answers

Study Notes

Bone Structure

Bone is a living organ that undergoes changes throughout an animal's life.
It consists of cells, collagen, glycoproteins, and calcium hydroxyapatite.
There are two types of bone formation: endochondral and intramembranous.

Bone Cells

Osteoclasts: cells that erode bone, used to remodel bone not needed, and extract calcium from bones.
Bone Lining Cells (BLCs): cover inactive bone surfaces, prevalent in the adult skeleton, and connect to other BLCs via gap junctions.

Endochondral Formation

All bones, except for the skull, undergo endochondral formation.
Bones begin as cartilage during fetal development, which is replaced by osteocytes and calcium hydroxyapatite.
Formation begins in the primary growth center in the diaphysis and expands outwards.
Cartilage is gradually removed as bone is created, and secondary growth begins in the epiphysis.

Bone Healing

Bones are one of the best healing tissues.
Fractures are most common in long bones.
The healing process involves haemorrhaging, hematoma, calluses, and remodelling.
Remodelling occurs after the callus has formed, and three factors influence healing.

Parathyroid Hormone (PTH)

Released by cells in the parathyroid gland.
Increases osteoclast activity, releasing calcium into blood circulation.
Inhibits osteoblast activity, reducing calcium deposition.
Increases the rate of excretion of inorganic phosphate by kidneys.

Vitamin D3 and Calcitriol

Vitamin D3 is an inactive precursor of calcitriol.
Calcitriol promotes intestinal absorption of calcium.
Stimulates osteoclast activity.

Calcitonin

Has the opposite effect to PTH and calcitriol.
Decreases osteoclast activity, reducing calcium release from bone.
Increases osteoblast activity, resulting in calcium deposition.

Spinal Column

Consists of vertebrae, which have bodies, arches, transverse and spinous processes, and vertebral foramina.
Between each vertebra are vertebral discs, which act as shock absorbers and allow for flexibility.
Processes are sites for muscle attachment and provide leverage for movement.

Regions of the Spinal Column

Cervical (C1-C7): atlas (C1) holds up the head and allows for nodding movement.
Thoracic (T1-T13): dorsal to the thorax, has the same number of vertebrae as ribs present.
Lumbar (L1-L7): dorsal to the abdomen, has large bodies to support abdominal organs.
Sacral (S1-S3): dorsal to the pelvic region, three vertebrae fused together to form the sacrum.

Pelvic Limb

Consists of the pelvis, femur, patella, fabellae, tibia, fibula, tarsus, metatarsus, and phalanges.
The pelvis develops as six bones that ossify into a complete structure.
The two halves of the pelvis are joined ventrally by the pelvic symphysis.
The pelvis joins the axial skeleton via the sacroiliac joints.

Pelvis

Hind limbs attach to the spinal column via the pelvis.
Functions: weight-bearing from hind limbs, protects and supports the intestines, bladder, and internal sex organs.
Notable structures: pelvic/pubic symphysis, acetabulum, obturator foramina.

Femur

Long bone of the thigh.
Proximal end: head of femur, large processes.
Straight shaft.
Distal end: forms the stifle joint with the patella and tibia.

Patella

Sesamoid bone, formed in the distal tendon of the quadriceps femoris muscle.
Protects the tendon as it passes over the trochlea.
Inserts on the tibial crest.

Tibia and Fibula

Tibia: main weight-bearing bone of the lower leg, proximally articulates with the femur to form the stifle joint.
Fibula: thin bone that parallels the tibia, serves as a muscle attachment site.

Tarsus and Metatarsus

Tibia and fibula articulate with the talus in the proximal tarsus.
Distal to the talus is the central tarsal bone, and then the smaller tarsal bones.
Tarsal bones: two rows of short bones, proximal row is named, and distal row is numbered.

Phalanges

Similar to the metacarpal bones, but with only four digits.
Almost exactly the same as in the thoracic limb.

The Pelvic Limb in Different Animals

Small mammals: have specific adaptations, such as rabbits having a separate bone named os acetabuli.
Guinea pigs: have a fibrocartilaginous suture line at the pubis and ischium, which allows separation of the pelvis prior to and during parturition.
Birds: have separate pubis bones that do not meet in the midline, and the pelvis fuses dorsally with the synsacrum.
Reptiles: have specific adaptations, such as chelonians having a rotated pelvis with the ilium near vertical.

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