Chapter 37 Biology
Key Terms for Section 1
Epithelial Tissue: There are many different kinds of epithelial tissue. Epithelial tissue lines most
body surfaces and it protects tissues from dehydration and psychical damage. An epithelial layer
is usually no more than a few cells thick. These cells are typically flat and thin, and they only
contain a small amount of cytoplasm. Epithelial tissue is constantly being replaced as cells die.
Nervous Tissue: The nervous system is made of nervous tissue. Nervous tissue consists of nerve
cells and their supporting cells. Nerve cells carry information throughout the body.
Connective Tissue: Various types of connective tissue support, protect, and insulate the body.
Connective tissue includes fat, cartilage, bone, tendons, and blood. Some connective tissue cells,
such as those in bone, are densely packed. Others, such as those found in blood, are farther apart
from each other.
Muscle Tissue: Three types of muscle tissue enable the movement of body structures by muscle
-Skeletal muscle is called voluntary muscle because you can consciously control its contractions.
Skeletal muscles move bones in the trunk and limbs.
- Smooth muscle is called involuntary muscle because you cannot consciously control its slow,
long-lasting contractions. Smooth muscles line the walls of blood vessels and hollow organs.
Some contract only when stimulated by signal molecules, others contract spontaneously.
-Cardiac muscle is involuntary and found in the heart. The powerful, rhythmic contractions of
cardiac muscle pump blood to all body tissues. Groups of cardiac cells contract all at once,
stimulating adjacent groups of cells to contract.
Body Cavity: The body contains four large fluid-filled spaces, or body cavities, that house and
protect the major internal organs. Within the body cavities, organs are suspended in fluid that
supports their weight and prevents them from being deformed by body movements. These organs
are also protected by bones and muscles.
-For example, your heart and lungs are protected by the rib cage and the sternum inside your
-Your brain, encased within the cranial cavity, is protected by the skull.
-Your digestive organs, located in the abdominal cavity, are protected by the pelvis and
-Your spinal cord is protected by the vertebrae that surround the spinal cavity.
Section 1 Review
1. From least to greatest size, the four levels of structural organization in the body are: cells,
tissues, organs, and organ systems. Cells the basic units of life, and they make up tissues, which
work in combination of at least two to make organs, which work in combinations to make organ
systems which support one or a few processes necessary for human life.
2. Epithelial: Skin Nervous: Certain cells in the brain
Connective: fat, cartilage, bone, tendons, and blood Muscle: Biceps, Cardiac muscle
3. Organs work in combination to make organ systems, which take care of vital processes
humans need to survive such as removing waste from the system.
4. As an endotherm, you can remain active at temperatures that would normally hinder a
ectotherm’s performance. Being an endotherm also allows you to sustain extraneous activity for
a long time.
5. Fevers raise the body temperature, which in turn sometimes inactivate critical enzymes for
survival. If someone has a fever for too long, their body could start slowly shutting down
because it cannot use certain critical enzymes.
6. C. Digestive tract lining
Key Terms for Section 2
Axial Skeleton: Out of the 206 bones in the human body, 80 of them form the axial skeleton,
which include the bones of the skull, spine, ribs, and sternum.
Appendicular Skeleton: The other 126 bones in the body form the appendicular skeleton.
Bone Marrow: Some cavities in spongy bone are filled with a soft tissue called bone marrow.
Red bone marrow begins the production of all blood cells and platelets. The hollow interior of
long bones is filled with yellow bone marrow though. Yellow bone marrow consists mostly of
fat, which stores energy.
Periosteum: Bones are surrounded by a tough exterior membrane called the periosteum. The
periosteum contains many blood vessels that supply nutrients to bones.
Haversian canal: In compact bone, new bone cells are added in layers around narrow, hollow
channels called Haversian canals. Haversian canals extend down the length of a bone, and they
contain blood vessels that enter the bone through the periosteum.
Osteocyte: Eventually in bone growth, bone cells called osteocytes become embedded within the
bone tissue. Osteocytes maintain the mineral content of bone. The blood vessels that run through
Haversian canals supply the osteocytes with nutrients needed to maintain blood cells.
Osteoporosis: Around the age of 35, bone replacement processes gradually become less efficient
and some bone tissue is lost. Severe bone loss can lead to a condition called osteoporosis, which
means “porous bone”. Bones affected by osteoporosis become brittle and are easily fractured.
Joint: Where two bones meet. Pads of cartilage cushion the ends of the bones of a joint, enabling
the joint to withstand great pressure and stress.
Ligament: The bones of a joint are held together by strong bands of connective tissue called
ligaments. Ligaments not only help stabilize joints, but also prevent joints from moving too far in
any one direction. Many sports-related injuries to ligaments are caused by an impact that forces a
joint to overextend. Injury occurs because the impact exceeds the tension that the ligaments can
Section 2 Review
1. The axial skeleton contains 80 bones out of the 206 total that contain the bones of the
skull, spine, ribs, and sternum. The appendicular skeleton contains the other 126 bones,
and consists of the appendages (or limbs)-the shoulders, arms, hips, and legs.
2. Compact bone has compact tight cells and is hard, and spongy bone is porous. Compact
bone is on the outside and spongy bone is on the inside.
3. Cartilage is gradually replaced by bone as minerals are deposited.
4. Immovable joints, cranial joints. S0lightly movable joints, spine vertebrae. Freely
movable joints, saddle joint.
5. Their bones are weaker in the first place, and not as big. And after menopause certain
hormones production rates drop.
6. Easier to make their way out of the birth canal. Also, they aren’t as heavy.
Key Terms for Section 3
Tendon: Muscles can move body parts because muscles are attached to the bones of the
skeleton. Most skeletal muscles are attached to bones by strips of dense connective tissue called
tendons. One attachment of the muscle, the origin, is a bone that remains stationary during a
muscle contraction. The muscle pulls against the origin. The other attachment, the insertion, is
the bone that moves when the muscle contracts. Movement occurs when a muscle contraction
pulls the muscle’s insertion toward its origin.
Flexor: A flexor muscle causes a joint to bend.
Extensor: An extensor muscle causes a joint to straighten.
Actin and Myosin (not always grouped): Protein filaments that enable muscles to contract.
Actin and Myosin are usually found in the cytoskeleton of eukaryotic cells, but they are far more
abundant in muscle cells. The thin filaments are actin, and the thick filaments are myosin.
Myofibril: Skeleton muscle tissue consists of many parallel elongated cells called muscle fibers.
Each muscle fiber contains small cylindrical structures called myofibrils. Myofibrils have
alternating light and dark bands that produce a characteristic striated, or striped, appearance
when viewed under a microscope. In the center of each light band is a structure called a Z line,
which anchors actin filaments.
Sarcomere: The area between two Z lines. This, a myofibril is a grouping of sarcomeres linked
end to end. Each sarcomere contains overlapping thin and thick protein filaments that move and
interact with each other. The dark bands that occur in the middle of the sarcomere are regions
where the thick filaments and the thin filaments overlap.
Section 3 Review
1. There is usually a flexor and an extensor to straighten and bend a joint.
2. Standards Assessment