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PART III: MAINTENANCE OF THE HUMAN BODY
CHAPTER 11: HUMAN ORGANIZATION
LEARNING OUTCOMES
11.1 Types of Tissues
1. List the four major types of tissues found in the human body, and describe the location
and major features of each.
2. Describe the functions of each tissue type, including the roles of specific cell types and
cellular modifications within each tissue.
11.2 Body Cavities and Body Membranes
1. Know the two main cavities of the human body and how each can be further divided.
2. Compare and contrast the location(s) and function(s) of the different types of body
membranes.
11.3 Organ Systems
1. Describe the general function of each body system.
2. Provide several examples of how different organ systems work closely together.
11.4 Integumentary System
1. Identify the two main regions of skin, and how these are distinguished from the
subcutaneous layer.
2. Describe the function(s) of each of the major accessory organs of the skin.
11.5 Homeostasis
1. Define homeostasis, and describe why it is essential to living organisms.
2. Distinguish between positive and negative feedback mechanisms, and list specific
examples of each in the human body.
3. Discuss the roles of organ systems in maintaining homeostasis, and the health
consequences if homeostasis is disrupted.
LECTURE OUTLINE
11.1 Types of Tissues
A tissue is composed of similarly specialized cells that perform a common function in the body.
The tissues of the human body can be categorized into four major types: epithelial tissue,
connective tissue, muscular tissue, and nervous tissue. Cancers are classified according to the
type of tissue from which they arise.
Epithelial Tissue
Epithelial tissue consists of tightly packed cells that form a continuous layer. Epithelial
tissue covers surfaces and lines body cavities. It usually has a protective function but it
can also be modified to carry out secretion, absorption, excretion, and filtration.
Junctions between Epithelial Cells
The cells of a tissue can function in a coordinated manner when the plasma
membranes of adjoining cells interact. The junctions between cells help cells
function as a tissue.
Connective Tissue
Connective tissue binds organs together, provides support and protection, fills spaces,
produces blood cells, and stores fat. As a rule, connective tissue cells are widely
separated by a matrix.
Loose Fibrous and Dense Fibrous Tissues
Loose fibrous connective tissue supports epithelium and also many internal
organs. Tendons and ligaments are made up of dense fibrous connective tissue.
Adipose Tissue and Reticular Connective Tissue
In adipose tissue, the fibroblasts enlarge and store fat. Reticular connective
tissue forms the support meshwork of lymphoid tissue.
Cartilage
There are three types of cartilage distinguished by the type of fiber in the matrix.
Bone
Bone is the most rigid connective tissue. It consists of an extremely hard matrix.
Blood
Blood is unlike other types of connective tissue in that the matrix is not made by
the cells. Red blood cells carry oxygen to tissues; white blood cells fight
infection. Platelets are involved in clotting.
Muscular Tissue
Muscle tissue is composed of cells called muscle fibers that contain actin and myosin
filaments whose interaction accounts for movement. There are three types of muscle
tissue.
Nervous Tissue
Nervous tissue contains nerve cells called neurons. The nervous system has just three
functions: sensory input, integration of data, and motor output.
Neuroglia
In addition to neurons, nervous tissue contains neuroglia. Their primary function
is to support and nourish neurons.
11.2 Body Cavities and Body Membranes
The human body is divided into two main cavities: the ventral cavity and the dorsal cavity. The
ventral cavity is divided into the thoracic, abdominal, and pelvic cavities.
Body Membranes
Body membranes line cavities and the internal spaces of organs and tubes that open to the
outside. There are different types including mucous membranes, serous membranes,
synovial membranes, and the meninges.
11.3 Organ Systems
Organ systems work together in the body. In a sense, it is arbitrary to assign a particular organ to
one system when it also assists the functioning of many other systems.
Integumentary System
The integumentary system contains the skin. It has a protective function, synthesizes
vitamin D, collects sensory data, and helps regulate body temperature.
Cardiovascular System
The cardiovascular system consists of the heart, the blood, and the vessels that the blood
moves through. Blood transports nutrients and oxygen and removes waste molecules.
Lymphatic and Immune Systems
The lymphatic system protects the body from disease by purifying lymph and storing
lymphocytes. The immune system consists of all the cells in the body that protect us
from disease.
Digestive System
The digestive system consists of the mouth, esophagus, stomach, small intestine, and
large intestine, along with associated organs. It receives food and digests it into nutrient
molecules.
Respiratory System
The respiratory system consists of the lungs and the tubes that take air to and from them.
The respiratory system moves oxygen and carbon dioxide.
Urinary System
The urinary system contains the kidneys, the urinary bladder, and the tubes that carry
urine. The system rids the body of metabolic wastes.
Skeletal System
The bones of the skeletal system protect body parts. In addition, the skeletal system
stores minerals and produces blood cells.
Muscular System
Skeletal, cardiac, and smooth muscle are responsible for contractions that account for
movement of the body and its parts.
Nervous System
The nervous system consists of the brain, spinal cord, and associated nerves that allow
us to respond to both external and internal stimuli.
Endocrine System
The endocrine system consists of the hormonal glands, which secrete chemical
messengers called hormones that have a wide range of effects.
Reproductive System
The reproductive system has different organs in the male and female. It is responsible for
the continuance of the species.
11.4 Integumentary System
The skin and its accessory organs (nails, hair, oil glands, and sweat glands) are collectively called
the integumentary system.
Regions of the Skin
The skin has two regions: the epidermis and the dermis. The epidermis is made up of
epithelium. The dermis is a region of fibrous connective tissue beneath the epidermis.
Accessory Organs of the Skin
Nails, hair, and glands are structures of epidermal origin.
11.5 Homeostasis
Homeostasis is the relative constancy of the body’s internal environment.
Negative Feedback
Negative feedback is the primary homeostatic mechanism that keeps a variable close to a
particular value, or set point. A homeostatic mechanism has at least two components: a
sensor and a control center.
Mechanical Example
A home heating system is often used to illustrate how a more complicated
negative feedback mechanism works.
Human Example: Regulation of Body Temperature
The sensor and control center for body temperature are located in a part of the
brain called the hypothalamus.
Positive Feedback
Positive feedback is a mechanism that brings about an ever greater change in the same
direction.
Homeostasis and Body Systems
All systems of the body contribute toward maintaining homeostasis and, therefore, a
relatively constant internal environment.
The Transport Systems
The cardiovascular system and lymphatic system regulate tissue fluid
composition.
The Maintenance Systems
The respiratory system adds oxygen to and removes carbon dioxide from the
blood. The digestive system takes in and digests food. The liver and kidneys
help remove toxins from the blood. The urinary system also regulates blood
volume, salt balance, and pH.
The Support Systems
The integumentary, skeletal, and muscular systems protect the internal organs.
The Control Systems
The nervous system and the endocrine system regulate the other systems of the
body.
Disease
Disease is an abnormality or upset in the body’s normal processes.