Integumentary
system Structure and functions of skin
Skeletal System :
· Divisions
of skeletal system
· Types
of bone
Integumentary system Structure
and functions of skin:
The
integumentary system is the body's outermost system and is composed of the
skin, hair, nails, and associated glands. The skin is the largest organ of the
body and is responsible for protecting the body from external damage,
regulating body temperature, and providing a barrier against water loss.
The skin is composed of three
layers: the epidermis, dermis, and hypodermis. The epidermis is the outermost
layer of the skin and is composed mainly of keratinocytes, which produce a
tough, waterproof protein called keratin. The epidermis also contains
melanocytes, which produce the pigment melanin, and Langerhans cells, which are
involved in immune function.
The dermis is the middle layer
of the skin and is composed mainly of connective tissue. It contains blood
vessels, nerves, and specialized structures such as hair follicles, sweat
glands, and sebaceous glands. The dermis is responsible for providing
structural support to the skin and contains collagen and elastin fibers that
give the skin its elasticity and strength.
The hypodermis is the deepest
layer of the skin and is composed mainly of adipose tissue. It serves as an
energy store and insulation for the body.
The skin has several
functions, including:
- Protection:
The skin serves as a barrier between the body and the environment,
protecting the body from physical, chemical, and biological damage.
- Sensation:
The skin contains sensory receptors that allow us to feel touch, pressure,
temperature, and pain.
- Thermoregulation:
The skin helps regulate body temperature through the process of sweating
and vasodilation or vasoconstriction of blood vessels.
- Vitamin
D synthesis: The skin can synthesize vitamin D when exposed to sunlight.
- Excretion:
The skin can excrete waste products through the process of sweating.
- Immune
function: The skin contains specialized cells and molecules that help
protect the body from infection and disease.
Overall, the skin is a complex
organ that plays a vital role in maintaining the health and wellbeing of the
body.
Skeletal System :
The skeletal
system is the body's framework of bones, cartilage, and ligaments that provides
support, protection, and movement for the body. The human skeletal system is
composed of 206 bones, which are connected by joints and held together by
ligaments.
The skeletal system has several
functions, including:
- Support:
The skeletal system provides structural support for the body and helps
maintain its shape.
- Protection:
The bones of the skeletal system protect vital organs such as the brain,
heart, and lungs.
- Movement:
The skeletal system works with the muscular system to produce movement.
- Storage
of minerals: Bones serve as a reservoir for minerals such as calcium and
phosphorus, which are essential for many bodily functions.
- Hematopoiesis:
The bone marrow within some bones is responsible for the production of red
and white blood cells.
The skeletal system is divided
into two main parts: the axial skeleton and the appendicular skeleton. The
axial skeleton includes the skull, vertebral column, and ribcage, while the
appendicular skeleton includes the bones of the arms, legs, pelvis, and
shoulder girdle.
Bones are classified into four
categories based on their shape: long bones, short bones, flat bones, and
irregular bones. Long bones, such as the femur and humerus, are longer than
they are wide and are found in the arms and legs. Short bones, such as the
bones of the wrist and ankle, are roughly as wide as they are long. Flat bones,
such as the bones of the skull, provide protection and a broad surface area for
muscle attachment. Irregular bones, such as the vertebrae, have complex shapes
that do not fit into the other categories.
The skeletal system is
constantly remodeling, with old bone tissue being broken down and new bone
tissue being formed. This process is regulated by hormones, such as parathyroid
hormone and calcitonin, and is important for maintaining bone health and
strength.
Divisions of skeletal system:
The skeletal
system can be divided into two main divisions:
- Axial
Skeleton: The axial skeleton is composed of bones that are located along
the body's central axis. It includes the skull, vertebral column, and
ribcage.
The skull is composed of the
cranium and facial bones. The cranium is the part of the skull that encloses
and protects the brain, while the facial bones provide support and structure
for the face. The vertebral column is composed of 33 individual vertebrae that
are stacked on top of one another, separated by intervertebral discs. The
vertebral column provides support for the head and trunk and protects the
spinal cord. The ribcage is composed of 12 pairs of ribs that attach to the
thoracic vertebrae at the back and the sternum at the front. It helps protect
the heart, lungs, and other vital organs.
- Appendicular
Skeleton: The appendicular skeleton is composed of bones that are located
in the limbs and their attachments to the axial skeleton. It includes the
bones of the arms, legs, pelvis, and shoulder girdle.
The shoulder girdle is
composed of the clavicle and scapula, which attach the arms to the axial
skeleton. The bones of the arm include the humerus, radius, and ulna, while the
bones of the leg include the femur, tibia, and fibula. The pelvis is composed
of the ilium, ischium, and pubis bones, which provide a strong and stable base
for the spine and support the weight of the upper body.
Together, the axial and
appendicular skeleton provide the body with support, protection, and the
ability to move.
Types of bone:
There are
five main types of bone in the human body:
- Long
bones: Long bones are the longest bones in the body and are found in the
arms, legs, hands, and feet. They have a cylindrical shape and are made up
of a shaft (diaphysis) and two rounded ends (epiphyses). Examples of long
bones include the femur, humerus, and tibia.
- Short
bones: Short bones are roughly cube-shaped and are found in the wrists and
ankles. They provide stability and support for the body's weight. Examples
of short bones include the carpals in the wrist and the tarsals in the ankle.
- Flat
bones: Flat bones are thin, flat, and usually curved. They provide
protection for organs and a large surface area for muscle attachment.
Examples of flat bones include the ribs, sternum, and scapula.
- Irregular
bones: Irregular bones have complex shapes that don't fit into the other
bone categories. They are found in various locations throughout the body,
such as the vertebrae and facial bones.
- Sesamoid
bones: Sesamoid bones are small, round bones that are embedded in tendons.
They help to protect tendons from wear and tear and provide leverage for
muscles. The patella (kneecap) is the largest sesamoid bone in the body.
All bones are composed of a
combination of hard, dense cortical bone (also called compact bone) and spongy,
porous trabecular bone (also called cancellous bone). The outer layer of bone
is covered by a tough, fibrous membrane called the periosteum, and the inner
cavity of bones is filled with soft, spongy bone marrow, which is responsible
for producing blood cells.
