There are two main layers of the skin.
The first layer is the epidermis. The epidermis contains keratinocytes cells that produce keratin, a
protein that helps waterproof and protect the skin. It also has melanocytes which are pigment
cells that produce melanin, a dark pigment that absorbs ultraviolet light, shielding the genetic
material in skin cells from damage. The epidermis also has Merkel's cells disks which are touchsensitive cells found in the deepest layers of hairless skin. The epidermis has no blood vessels in
it. The epidermis consists of four layers, but the soles of the feet and palms of the hands have
five layers.
The next major layer is the dermis. It is the layer that is made up of connective tissue that
contains protein, collagen, and elastic fibers. It also contains blood vessels, sensory receptors,
related nerves, and glands. The functions of the dermis are to regulate body temperature with
sweat glands whose ducts pass through the epidermis to the outside and open on the skin surface
through pores. The dermis is also the site of hair with Hair follicles and hair roots. The dermis
also helps keep hair soft and hydrated with sebaceous glands that produce an oily substance
called sebum. The dermis also has the function of sensing the environment the body is in with
sensors that detect touch, heat, cold, pain and pressure.
A third part of the skin is the hypodermis, which is below the dermis, and is composed of fat or
other connective tissue.
Where the umbilical cord attaches in the mother.
The umbilical cord is a cord that connects a developing embryo or fetus to the placenta. The
umbilical cord contains three connections. Two of those connections are umbilical arteries which
supply deoxygenated blood from the fetus to the placenta in the umbilical cord. The third is an
umbilical vein which carries oxygenated blood from the placenta to the growing fetus.
How does the skin regulate the temperature and water loss from the body?
The skin regulates body temperature by sweating, constricting blood vessels, and expanding
blood vessels. If heat builds up in the body, sweat glands in the skin produce sweat that
evaporates and cools the skin. When the body becomes too hot, blood vessels in the skin expand
and bring more blood to the surface. This makes body heat slowly decrease. When the body is
too cold, the blood vessels in the skin contract, resulting in less blood at the body surface with
heat being conserved.
The skin regulates water loss by having Keratin (an insoluble protein in the outer layer of the
skin) help keep needed water in and using sweat glands to release sweat and riding the body of
unwanted moisture.
 Describe the structure of a bone and the different functions of each part.
Bones are made of two layers. The outer layer of bones is called the compact (cortical) bone.
This part of the bone is dense and has minimal gaps and spaces. The function cortical bones are
to support the whole body, protect organs, and provide levers for movement. In the compact
bone, bone surrounds blood. The interior of bones is called trabecular (cancellous or spongy)
bone. This is where blood vessels and marrow reside. New blood cells are created in bone
marrow and are then circulated by the blood vessels.
Long Bone:
The outside of the bone consists of a layer of connective tissue called the periosteum. The outer
layer of the long bone is compact bone, then a deeper layer of cancellous bone (spongy bone)
which contains red bone marrow. The interior part of the long bone is the medullary cavity (the
place where red or yellow marrow is stored) with the inner core of the bone cavity being
composed of yellow marrow. The function of a long bone is to provide structure for the body and
movement.
Flat Bone:
Flat bones consist of two thin layers of compact bone that enclose a thin layer of cancellous
bone, which is the location of red bone marrow. In an adult, most red blood cells are formed in
flat bones.
The functions of flat bones are: to protect vital softer and also provide a surface for muscle
attachments.
Flat bones include: the scapula, the hip bone, and ribs
There are three types of muscle: skeletal, cardiac, and smooth muscle.
Skeletal muscle is attached to the skeleton and moves the body. Skeletal muscle is also is under
voluntary control. There are two types of skeletal muscles (which can be fast twitch or slow)
twitch: red and white. Red muscle has high levels of myoglobin and oxygen storing proteins.
Red muscle fibers also tend to have more mitochondria and blood vessels than the white ones.
White muscle has less concentration of myoglobin and oxygen storing proteins. Fast twitch
fibers have that myosin can split ATP very quickly. Slow twitch fibers make energy for ATP resynthesis a long term system of aerobic energy transfer.
Cardiac muscle is only located in the heart and is not normally under voluntary control. Cardiac
muscle has striations (stripes) formed by alternating segments of thick and thin protein filaments.
The actin filaments are thin while the myosin filaments are thick.
Smooth muscle surrounds blood vessels and other passageways and contracts or expands
openings or passageways and propels material through body tubes. Smooth muscle exists
throughout the body and is involuntary controlled. The respiratory and digestive tracts have
layers of smooth muscle in their walls. Smooth muscle contracts entirely with the help of
molecules myosin and actin.
 Describe the structure and function of three types of joints