Therefore, their offspring also had pelvic anatomy that enabled successful childbirth Figure The lower limb consists of the thigh, the leg, and the foot. The bones of the lower limb are the femur thigh bone , patella kneecap , tibia and fibula bones of the leg , tarsals bones of the ankle , and metatarsals and phalanges bones of the foot Figure The bones of the lower limbs are thicker and stronger than the bones of the upper limbs because of the need to support the entire weight of the body and the resulting forces from locomotion.
In addition to evolutionary fitness, the bones of an individual will respond to forces exerted upon them. The femur , or thighbone, is the longest, heaviest, and strongest bone in the body. The femur and pelvis form the hip joint at the proximal end. At the distal end, the femur, tibia, and patella form the knee joint. The patella , or kneecap, is a triangular bone that lies anterior to the knee joint.
The patella is embedded in the tendon of the femoral extensors quadriceps. It improves knee extension by reducing friction. The tibia , or shinbone, is a large bone of the leg that is located directly below the knee. The tibia articulates with the femur at its proximal end, with the fibula and the tarsal bones at its distal end.
It is the second largest bone in the human body and is responsible for transmitting the weight of the body from the femur to the foot. The fibula , or calf bone, parallels and articulates with the tibia. It does not articulate with the femur and does not bear weight. The fibula acts as a site for muscle attachment and forms the lateral part of the ankle joint. The tarsals are the seven bones of the ankle. The ankle transmits the weight of the body from the tibia and the fibula to the foot.
The metatarsals are the five bones of the foot. The phalanges are the 14 bones of the toes. Each toe consists of three phalanges, except for the big toe that has only two Figure The transition of vertebrates onto land required a number of changes in body design, as movement on land presents a number of challenges for animals that are adapted to movement in water. The buoyancy of water provides a certain amount of lift, and a common form of movement by fish is lateral undulations of the entire body.
This back and forth movement pushes the body against the water, creating forward movement. In most fish, the muscles of paired fins attach to girdles within the body, allowing for some control of locomotion. As certain fish began moving onto land, they retained their lateral undulation form of locomotion anguilliform.
However, instead of pushing against water, their fins or flippers became points of contact with the ground, around which they rotated their bodies. The effect of gravity and the lack of buoyancy on land meant that body weight was suspended on the limbs, leading to increased strengthening and ossification of the limbs.
The effect of gravity also required changes to the axial skeleton. Lateral undulations of land animal vertebral columns cause torsional strain. In later tetrapods, the vertebrae began allowing for vertical motion rather than lateral flexion. Another change in the axial skeleton was the loss of a direct attachment between the pectoral girdle and the head.
This reduced the jarring to the head caused by the impact of the limbs on the ground. The vertebrae of the neck also evolved to allow movement of the head independently of the body.
The appendicular skeleton of land animals is also different from aquatic animals. The shoulders attach to the pectoral girdle through muscles and connective tissue, thus reducing the jarring of the skull. This type of motion requires large muscles to move the limbs toward the midline; it was almost like walking while doing push-ups, and it is not an efficient use of energy.
Later tetrapods have their limbs placed under their bodies, so that each stride requires less force to move forward. This resulted in decreased adductor muscle size and an increased range of motion of the scapulae. This also restricts movement primarily to one plane, creating forward motion rather than moving the limbs upward as well as forward.
The femur and humerus were also rotated, so that the ends of the limbs and digits were pointed forward, in the direction of motion, rather than out to the side. By placement underneath the body, limbs can swing forward like a pendulum to produce a stride that is more efficient for moving over land.
The three types of skeleton designs are hydrostatic skeletons, exoskeletons, and endoskeletons. A hydrostatic skeleton is formed by a fluid-filled compartment held under hydrostatic pressure; movement is created by the muscles producing pressure on the fluid.
An exoskeleton is a hard external skeleton that protects the outer surface of an organism and enables movement through muscles attached on the inside.
An endoskeleton is an internal skeleton composed of hard, mineralized tissue that also enables movement by attachment to muscles. The human skeleton is an endoskeleton that is composed of the axial and appendicular skeleton. Description Classroom Ideas. Description up. This clip is from : Science Clips , Moving and Growing. Animals Wild Cities Wild parakeets have taken a liking to London. Animals Wild Cities Morocco has 3 million stray dogs.
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Subscriber Exclusive Content. Why are people so dang obsessed with Mars? How viruses shape our world. The skeletons of humans and horses are examples of endoskeletons. An endoskeleton is a skeleton that consists of hard, mineralized structures located within the soft tissue of organisms. An example of a primitive endoskeletal structure is the spicules of sponges. The bones of vertebrates are composed of tissues, whereas sponges have no true tissues Figure 3.
Endoskeletons provide support for the body, protect internal organs, and allow for movement through contraction of muscles attached to the skeleton.
The human skeleton is an endoskeleton that consists of bones in the adult. It has five main functions: providing support to the body, storing minerals and lipids, producing blood cells, protecting internal organs, and allowing for movement.
The skeletal system in vertebrates is divided into the axial skeleton which consists of the skull, vertebral column, and rib cage , and the appendicular skeleton which consists of the shoulders, limb bones, the pectoral girdle, and the pelvic girdle. The three types of skeleton designs are hydrostatic skeletons, exoskeletons, and endoskeletons.
A hydrostatic skeleton is formed by a fluid-filled compartment held under hydrostatic pressure; movement is created by the muscles producing pressure on the fluid.
An exoskeleton is a hard external skeleton that protects the outer surface of an organism and enables movement through muscles attached on the inside.
An endoskeleton is an internal skeleton composed of hard, mineralized tissue that also enables movement by attachment to muscles.
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