Topic 4: Tissues, organ Systems, and homeostasis  (09052012 NK)


Dictionary of Terms


Review Quiz

Pictures of tissue types




1)     Name the four types of tissues.

2)     Describe the location and the purpose of Epithelial tissue.

3)     Describe the location and the purpose of Connective tissue.

4)     Describe the location and the purpose of Muscle tissue.

5)     Describe the location and the purpose of Nervous tissue.

6)     Describe what an organ is.

7)     Describe what an organ system is.

8)     what  are the functions of skin.

9)     How do multicellular organisms maintain homeostasis?

10)  Describe a typical positive feedback response.


Useful figures

4.1,2,3, the 11 organ system figures 4.10 skin and 4.12 components of a negative feedback control.


1.  The function of the body dictates its structure. 

A.  The human body is programmed to:

1)   Maintain internal operating conditions (temperature, salinity, pH) within some tolerable range. (Homeostasis)

2)   Locate and acquire nutrients and dispose of waste (eat and poop)

3)   Protect itself against injury or attack from accidents, viruses, bacteria, and other agents

4)   Reproduce and provide for the health and safety of our offspring during early development

5)   Laugh at bad jokes

B.  Our body is the sum of it’s smaller parts.  The following is a list of the 4  levels of organization in we humans

1)   Tissues (The 4 types are- epithelial, connective, muscle, nervous) are an aggregation of cells and extracellular substances functioning for a specialized activity.

2)   Various types of tissues can combine to form functional units called organs, (like th heart, kidneys and brain)

3)   Organs may interact to form organ systems such as the digestive system, where multiple organs work in concert to perform a single function, like digestion.

4)   From molecules to cells to tissues to organs to organ systems to a body,  Each part of the body has properties that depend on its subunits.

C.  The structure that we see depends a lot on the function.  Just like a racecar is sleek and sporty and looks like it is designed for speed so to the parts of our body share a form that is dictated by their function.


List of tissues and their subtypes


Membranous, Glandular


Conductive, supportive


Cardiac, skeletal, smooth


Proper, blood, bone, cartilage


We will now cover the four types of tissues that make up the human body

1.   Epithelial tissue                                                               top

A.  Epithelial tissue is commonly called epithelium

1)   Cells of the epithelium are linked tightly together: there may be one or more layers

2)   One surface is free and unattached(facing the outside of the body) and the other adheres to a structure called the basement membrane: specialized junctions form links between epithelial cells

3)   The 4 types of epithelium are named according to their shapes

a)   Simple epithelium is a single layer of cells functioning as a lining for body cavities, ducts, and tubes

b)   Squamous epithelium consists of flattened cells, examples are found in the lining of the blood vessels

c)   Cuboidal epithelium has cube shaped cells,: examples are found in glands that secrete substances

d)    Columnar epithelium has elongated cells: examples are found in the intestine

4)   Stratified epithelium has many layers--as in the human skin

5)   Pseudostratified epithelium is a single layer of cells that looks like a double layer, most of the cells are ciliated: examples are found in the respiratory passages and reproductive tracts

6)   Glandular epithelium

a)   Glands are secretory structures derived from epithelium in which goblet cells (mucus producing) are embedded

b)   Glands are classified according to how their products reach the site where they are used

(1)Exocrine glands often secrete their product through ducts to a free surfaces: they secrete mucus, saliva, earwax, milk, oil and digestive enzymes

(a)  Simple exocrine glands have only a few branches

(b)Compound glands have many branches

(c) Apocrine glands (e.g. mammary) include bits of gland cells in their secretions

(d)Holocrine glands (e.g. oil) whole cells are released which may later release the secretions inside the duct

(e) Merocrine glands (e.g. salivary) do not include cell elements in their secretions.

(2)Endocrine glands have no ducts, but distribute their product (hormones) via the blood

B.  Membranes made of epithelium (do not confuse this with the cell membrane J)

1)   Mucus membranes line the tubes and cavities of the digestive, respiratory, and reproductive systems where embedded glands secrete mucus that act as lubricants

2)   Serous membranes such as those that line the thoracic cavity do not contain glands, they also produce lubricants

C.  Cell to Cell contacts in Epithelium  (How cells are held together)

1)   Epithelial cells tend to adhere to one another by means of specialized attachment sites

a)   Tight junctions link cells of epithelial tissues to form seals that keep molecules form freely crossing the epithelium, without tight junctions solutions would flow around the cells into the body

b)   Adhesion junctions or desmosomes are like spot welds in tissues subject to stretching (the bladder)

c)   Gap  junctions link the cytoplasm of adjacent cells: they form communication channels.

2)   Sites of cell to cell contact are especially profuse when substances must not leak form one body compartment to another  (certain parts of the body are designed to leak)

2.   Connective tissues (this tissue fills up empty spaces, glues other body tissue together, forms support)

A.  General characteristics of connective tissue

1)   Most connective tissue contains fibroblasts which are cells that secrete fibers made of collagen or elastin

2)   The fibers are embedded in a jelly like ground substance, which forms the extracellular matrix surrounding the embedded cells

3)   Depending on the number of cells and the thickness of the ground substance connective tissue can be liquid like blood or solid like bone.

B.  Connective Tissue Proper

1)   Loose connective tissue supports epithelia and organs and surrounds blood vessels and nerves: it contains more cells and fewer, thinner fibers

2)   Dense irregular connective tissue has fewer cells and more fibers which are thick: it forms protective capsules around organs

C.   Specialized connective tissue

1)   Dense, regular connective tissue has bundled collagen fibers lying in parallel and is found in ligaments (binding bone to bone) and tendons (binding muscle to bone)

D.  Cartilage and Bone

1)   Cartilage contains a dense array of fibers in a rubbery ground substance (matrix) produced by chondroblasts, which mature into chondrocytes located in lacunae. 

a)   Hyaline cartilage has many small fibers: it is found at the ends of bones, in the nose, ribs and the windpipe

b)    Elastic cartilage, because of its elastin component, is able to bend yet maintain its shape such as the external ear

c)    Firbocartilage is a sturdy and resilient form that can withstand pressure such as in the disks that separate the vertebrae

2)    Bone is organized as flat plates and cylinders, bones support and protect body tissues and organs: they also work with muscles to perform movement

a)   The bone matrix is mineralized (calcium) and hardened, but includes little holes or lacunae for the osteocytes (bone producing cells)

b)    Compact bone appear to be very solid and makes up the shafts and long bones and the outer regions of all bones

c)    Spongy bone occurs inside bones and includes large, marrow filled spaces

E.    Blood and adipose tissue

1)   Blood

a)   Blood is a fluid tissue derived from connective tissue.

b)    The fluid plasma contains suspended formed elements: red blood cells (oxygen transport), white cells (defense) and platelets (clotting).

c)   Blood transports oxygen, wastes, hormones and enzymes.

2)   Adipose tissue

a)   Adipose tissue cells are specialized for the storage of fat, which can be used as an energy reserve and cushions to pad organs.

b)    Adipose has a rich supply of blood vessels, which serve as highways for the movement of fats to and from individual adipose cells.

3.   Muscle tissue

A.  Muscle tissue contracts in response to stimulation, then passively lengthens (does not require energy)  **** Note muscle tissue can only pull, it cannot push *****

B.  There are three types of muscle;

1)   Skeletal muscle tissue attaches to bones (via tendons) for voluntary movement: it contains striated (actin and myosin) multinucleated, long cells (fibers which are often bundled together to form a “muscle”.

2)   Smooth  muscle tissue contains spindle shaped cells with a single nucleus: it lines the gut, blood vessels and glands its operation is involuntary.

3)    Cardiac (heart) muscle is composed of short, striated cells that can function in units due to the contracting signal that passes from cell to cell by way of the gap junctions.

4.    nervous tissue

A.  Neutron Structure

1)   Neurons, and associated neuroglia cells, are organizes as lines of communication throughout the body.

2)   Branched dendrites pick up chemical messages and pass them to an outgoing axon

3)    Communication between neurons is by chemical neurotransmitters, such an acetylcholine.

4)   A nerve is a bundle of neuron processes conduct to and from the CNS.

B.  Neuron functions

1)   Sensory neurons pick up stimuli and conduct to the central nervous system

2)   Motor neurons conduct impulses to muscles and glands

5.   Organ systems  (11, you should know most of them already)

A.   Many of the more complex functions of the human body cannot be performed by a single tissue alone.  An Organ is a structure composed of two or more tissue types  joined together to perform a specific function.  However even this complex organ cannot perform many of the general functions of the body.

B.  Eleven organ systems (integumentary, muscular, skeletal, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive) sorry just memorize the.   These all contribute to the survival of all the living cells of the body.  We will be covering each of these organ systems for the remainder of the class.

C.  The holes in the body are as important as what makes up the body.  The major cavities of the human body are: cranial, spinal, thoracic, abdominal, and sometimes pelvic.  They provide a location for many of the organ systems, so that these systems can move and act independently of the rest of the body.

6.   The Skin: What is it and how does it work and why it is important

A.   Humans have an outer covering called the integument, which includes the skin and the structures derived form epidermal cells such as nails.

B.  Skin function

1)   The skin covers and protects the body form abrasion, bacterial attack, ultraviolet radiation and dehydration.

2)    It helps control internal temperature.

3)    Its vessels serve as blood reservoir for the body.

4)    The skin produces vitamin D.

5)   Its receptors are essential in determining environmental stimuli. Touch, vibration, pain and temperature.

6)   It regulates the movement of substance into and out of the body or somatic system.

C.  Skin Structure

1)   Epidermis refers to the thin, outermost layers of cells consisting of stratified, Squamous epithelium

a)    Keratinization of epidermal cells of the stratum corneum turns them into dead bags of keratin, a waterproofing protein.

b)   Three pigments--melanin, hemoglobin, and carotene--contribute to skin color.  Dermis, the ticker portion of the skin underlying the epidermis, is mostly dense connective tissue

(1)Blood vessels, lymph vessels, and nerve endings are located here

(2)Sweat glands secrete a fluid (mostly water with a little dissolved salt) that is useful in regulating the temperature of the body

(3)Oil (sebaceous) glands function to soften and lubricate the hair and skin: acne is a condition in which the ducts become infected by bacteria

(4)Hairs are flexible structures rooted in the skin and projecting above the surface, growth is influence by genes, nutrition ,a d hormones

(5)As the body ages, epidermal cells divide less often, skin becomes thinner, more susceptible to injury, drier and less elastic.

7.    Homeostasis and Systems Control

A.  The internal environment

1)   The trillions of cells in our bodies must be continuously bathed in fluid that supplies nutrients and carries away metabolic wastes.

2)   The extracellular fluid consists of interstitial fluid (between the cells and tissues) and plasma (blood fluid).

3)   The component parts of an animal work together to maintain the stable fluid environment required for life

B.  Mechanisms of Homeostasis

1)   Homeostatic mechanisms operate to maintain chemical and physical environments within tolerable limits these are often called the controlled variable and can include

a)   Blood pressure

b)   Body temperature

c)   Blood glucose

2)   Homeostatic control mechanisms require three components:

a)   Sensory receptor cells detect specific changes in the environment

b)   Integrators or control centers (brain and spinal cord) act to direct impulses to the place where a response can be made

c)   Effectors (muscles and glands) perform the appropriate response

3)   A common homeostatic mechanism is negative feedback.

a)   It works by detecting a change in the internal environment that brings about a response that tends to return donations to the original state.

b)   It is similar to the functioning of a thermostat in a heating/cooling system.

4)   Positive feedback mechanisms may intensify the original signal: sexual arousal is an example, childbirth and blood clotting.    

a)   It is important to note that positive feedback is not a mechanism for maintaining homeostasis.


Possible assignments: things to think about

1.      What are the typical parts of a tissue?

2.      What distinguishes one type of tissue from another?

3.      Why is blood (a liquid considered) a connective tissue?

4.      Why are organ systems necessary?

5.      Is one organ system more important than any others?

6.      Rising blood sugar levels after a meal normally trigger insulin secretion, which in turn causes glucose to be converted to glycogen for storage.  How is this similar to the response of an air conditioner thermostat to rising room temperature

7.      How would you answer someone who says, “people in the tropics have such dark skin because they are out in the sun a lot making their skin tan fast and heavily.”


 Multiple Choice Questions:  Click on the revolving arrow to go to the study link


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1.   A tissue can be described as a number of different types of cells that come together to perform a common function.  Which of the following tissues are correctly matched with their functions?


A.   Epithelial tissue forms a protective coating on most organs and is the place where nutrients move in and out of various parts of the body

B.  connective tissue provides fillers for other tissues and organs it supplies nutrients and protects various organs

C.  muscle tissue responds to various stimuli and becomes longer in response

D.  Support tissue is like the electrical wiring of the body.  It transfers a stimulus from one portion of the body to the other.

E.   Adipose tissue makes up the thinking organs like the brain

Review this topic


2.   What type of epithelial tissue typically forms single layers of cells that line body cavities, ducts and tubes?

Simple epithelium

Cuboidal epithelium

 Squamous epithelium     

Columnar epithelium





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3.    Which of the following would be a significant difference between epithelial and connective tissues?

A.   Only Epithelial tissues have cells

B.   Only epithelial tissues have a ground substance

C.   Only epithelial tissues are arranged in sheets with special junctions between cells that are side by side

D.   Only connective tissues have a ground substance

E.    Only connective tissues have cells

Review epithelial                             Review connective


4.   Which of the following activities can be performed by muscle tissue

A.  Provides a soft substance that can be worked on

B.  When placed between two blocks it will pull the blocks together

C.  When placed between two blocks it will push the blocks apart

D.  Will conduct a signal form one part of the body to another.

E.   Will store food and form a cushion with the organs.

Review Muscle activity

5.   The outermost layer of cells that make up the skin is called

A.  The epidermis and it is made up of simple epithelium

B.  The epidermis and it is made of squamous epithelium

C.  The dermis and it is mainly dense connective tissue

D.  The melanin within this layer gives the skin its color

E.   Hemoglobin it is made of squamous epithelium








Answers 1) a,b,d 2) a 3)c,d 4)b 5) b





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