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Name: _____________________________ Class: _________________ Date: __________________
SECTION
33.2
MUSCULAR SYSTEM
Reinforcement
KEY CONCEPT Muscles are tissues that can contract, enabling movement.
The muscular system is the body system that moves things in and through your body.
Muscles are composed of muscle fibers, which are cells that contract, or shorten, when
they are stimulated by the nervous system. There are three types of muscle:
•
Skeletal muscle is a striped tissue that is attached to bones by long bands of
connective tissue called tendons. This muscle allows you to move your arms
and legs.
•
•
Muscle that lines organs and tissues in your body is called smooth muscle.
Smooth muscle pushes food through your digestive system and regulates the width
of blood vessels.
Your heart, which is made up of cardiac muscle, pumps blood throughout your
body.
Within a muscle are many long strands of protein called myofibrils. These protein
strands contain many smaller structures which allow the muscle to pull or contract. Tiny
f ilaments within the myofibril will actually cause the muscle contraction. A sarcomere
is a microscopic section of muscle that contains all of the filaments necessary to cause a
portion of a cell to contract. One filament will pull the other and cause the muscle to
shorten.
Myosin is a thick filament that does the pulling action. Myosin is anchored to the center
of the sarcomere. As it pulls at a second filament called actin, the actin drags some
of the muscle cell behind it. This causes the sarcomere to shorten and the muscle to
contract.
1. What are the three types of muscle and what does each type move?
2. What is a sarcomere?
3. How do myosin and actin work to cause muscles to contract?
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Protection, Support, and Movement
Name: _____________________________ Class: _________________ Date: __________________
SECTION
INTEGUMENTARY SYSTEM
33.3
Reinforcement
KEY CONCEPT The integumentary system has many tissues that protect the body.
The integumentary system is the body system that includes the skin and the tissues
within the skin. The integumentary system has many structures that help you to
maintain homeostasis.
•
Oil glands prevent bacteria from growing on the skin.
•
•
Sweat glands allow the body to release excess heat by sweating.
Keratin is a protein that makes the skin tough so that bacteria cannot break
through. It also makes the skin waterproof.
The integumentary system includes three layers:
•
The epidermis is the outermost layer. It is made mainly of dead skin cells and
contains pores through which glands release sweat and oil. It also has some
protective proteins, such as keratin and melanin. Melanin is a pigment that blocks
harmful rays from the sun from reaching your internal organs.
•
The dermis is a second layer of skin. This layer includes blood vessels, glands,
structural proteins, and nerves. The dermis contains hair follicles, elongated pits
that produce the protein that forms hair.
•
The third layer is a layer of subcutaneous fat. This layer protects and cushions
blood vessels and nerves. It also insulates the muscles and internal organs from
changes in the outside temperature.
1. How do glands in the integumentary system help you to maintain homeostasis?
2. What is found in the dermis?
3. What are four structures found in the epidermis?
4. What is the role of the subcutaneous fat layer?
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Protection, Support, and Movement
Name: _____________________________ Class: _________________ Date: __________________
SECTION
REPRODUCTIVE ANATOMY
34.1
Reinforcement
KEY CONCEPT Female and male reproductive organs fully develop during puberty.
The reproductive system is a collection of specialized organs, glands, and hormones
that help to produce a new human being. Females and males reach sexual maturity only
after puberty. Puberty begins with the release of hormones such as follicle-stimulating
hormone (FSH) and luteinizing hormone (LH).
The main functions of the female reproductive system are to produce sex cells, or
ova, and to provide a place where a fertilized egg can develop. Female reproductive
organs are located within the body and include the ovaries, uterus, fallopian tubes,
and vagina. In the ovaries, FSH and LH stimulate the release of estrogen, a hormone
that helps to develop eggs and prepare the uterus to receive a fertilized egg. When an
egg matures, it is released from the ovary, travels through the fallopian tube where it
can be fertilized, and enters the uterus.
The main functions of the male reproductive system are to produce sperm cells and to
deliver them to the female reproductive system. Males do not produce sperm until after
puberty, but can produce sperm for the rest of their lives. Sperm production occurs in
the testes, where LH stimulates the production of an important hormone, testosterone.
The testes are enclosed in the scrotum to keep them cooler than body temperature.
Immature sperm leave the testes and travel through a duct known as the epididymus,
where they mature. During sexual stimulation, the sperm travel to the vas deferens,
where fluids from three glands help sperm move more easily. These fluids, together with
the sperm, form a whitish substance known as semen. During sexual arousal, the penis
becomes rigid, and semen is propelled along the urethra and ejected from the penis.
1. What are the main functions of the female and male reproductive systems?
2. Name the two hormones that help to develop ova and sperm?
3. Describe the path an egg travels once it leaves the ovaries.
4. Where are immature sperm found, and where do they mature?
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Protection, Support, and Movement
Name: _____________________________ Class: _________________ Date: __________________
SECTION
33.1
SKELETAL SYSTEM
Reinforcement
KEY CONCEPT The skeletal system includes bones and tissues that are important for
supporting, protecting, and moving your body.
The skeletal system is an organ system that includes your bones and the tissues that
connect your bones together.
•
The appendicular skeleton is the collection of bones that are found in your legs
and arms. These bones are the ones that allow you to move.
•
The collection of bones that supports your body weight and protects your internal
organs is called your axial skeleton. This includes your skull, rib cage, and the
vertebrae of your spinal column.
The place where two bones connect is called a joint. Joints that allow for some
movement have cartilage, a tough tissue, between the bones. Cartilage allows bones
to move over one another without wearing down their ends. Joints that have limited
movement, such as those found in the spine and the rib cage, are bound tightly by
cartilage. Joints that have a wide range of motion, such as those in the knee and elbow,
are connected by long bands of tissue called ligaments.
Bones, themselves, are living tissue. The outer most layer, compact bone, is very dense
and has cells and blood vessels found embedded in it. Underneath the compact bone is
spongy bone. Spongy bone is porous, and it contains bone marrow, which will either
store fat or produce red blood cells.
As people grow, so do their bones. Calcification is the process by which specialized
bones cells make hard compact bone.
The cells found within bone also play an important part in maintaining calcium
homeostasis in the body. For example, if the bloodstream is low on calcium, cells in the
bones remove calcium from the bones and make it available to the rest of the body. If
there is extra calcium in the blood, bone cells add some calcium to the bones. The more
calcium in the bones, the stronger they are.
1. What are the roles of the appendicular skeleton and the axial skeleton?
2. What are the two layers in bone?
3. How do bone cells affect the amount of calcium found in the bloodstream?
© Houghton Mifflin Harcourt Publishing Company
Holt McDougal Biology
Protection, Support, and Movement