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By the end of this section, you will be able to:
  • Describe epithelial tissues
  • Discuss the different types of connective tissues in animals
  • Describe three types of muscle tissues
  • Describe nervous tissue

The tissues of multicellular, complex animals are four primary types: epithelial, connective, muscle, and nervous. Recall that tissues are groups of similar cells group of similar cells carrying out related functions. These tissues combine to form organs—like the skin or kidney—that have specific, specialized functions within the body. Organs are organized into organ systems to perform functions; examples include the circulatory system, which consists of the heart and blood vessels, and the digestive system, consisting of several organs, including the stomach, intestines, liver, and pancreas. Organ systems come together to create an entire organism.

Epithelial tissues

Epithelial tissues cover the outside of organs and structures in the body and line the lumens of organs in a single layer or multiple layers of cells. The types of epithelia are classified by the shapes of cells present and the number of layers of cells. Epithelia composed of a single layer of cells is called simple epithelia    ; epithelial tissue composed of multiple layers is called stratified epithelia    . [link] summarizes the different types of epithelial tissues.

Different Types of Epithelial Tissues
Cell shape Description Location
squamous flat, irregular round shape simple: lung alveoli, capillaries stratified: skin, mouth, vagina
cuboidal cube shaped, central nucleus glands, renal tubules
columnar tall, narrow, nucleus toward base tall, narrow, nucleus along cell simple: digestive tract pseudostratified: respiratory tract
transitional round, simple but appear stratified urinary bladder

Squamous epithelia

Squamous epithelial cells are generally round, flat, and have a small, centrally located nucleus. The cell outline is slightly irregular, and cells fit together to form a covering or lining. When the cells are arranged in a single layer (simple epithelia), they facilitate diffusion in tissues, such as the areas of gas exchange in the lungs and the exchange of nutrients and waste at blood capillaries.

Illustration A shows irregularly shaped cells with a central nucleus. Micrograph B shows a cross section of squamous cells from the human cervix. In the upper layer the cells appear to be tightly packed. In they middle layer they appear to be more loosely packed, and in the lower layer they are flatter and elongated.
Squamous epithelia cells (a) have a slightly irregular shape, and a small, centrally located nucleus. These cells can be stratified into layers, as in (b) this human cervix specimen. (credit b: modification of work by Ed Uthman; scale-bar data from Matt Russell)

[link] a illustrates a layer of squamous cells with their membranes joined together to form an epithelium. Image [link] b illustrates squamous epithelial cells arranged in stratified layers, where protection is needed on the body from outside abrasion and damage. This is called a stratified squamous epithelium and occurs in the skin and in tissues lining the mouth and vagina.

Cuboidal epithelia

Cuboidal epithelial cells, shown in [link] , are cube-shaped with a single, central nucleus. They are most commonly found in a single layer representing a simple epithelia in glandular tissues throughout the body where they prepare and secrete glandular material. They are also found in the walls of tubules and in the ducts of the kidney and liver.

Questions & Answers

what is matter
Emmanuel Reply
matter is anything that has mass and can occupied space
Alice
weight
Alice
how the kidney functions as osmoregulatory organ
Sam Reply
That true
Banda
what is the major connection for sugars in glycolysis?
Ibrahim Reply
Simple term of science
Palesa Reply
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gopal
it's means what do u know about biology?
Phathu
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Melysa
the action of making a person immune to infections ,for immunisation
Kalia
what is the biology? what do you know about biology
Phathu Reply
biology is the study of living organisms, divided into many specialized fields that cover their morphology, physiology, anatomy, behavior, origin, and distribution.
Julia
The study of all aspects of life. The study of all living organisms (such as animal cells and plant cells) in greater detail (their structure and how they function). It's a very broad science.
juanita
what is prokaryotic
Bhaskar Reply
what is pathogens
Bhaskar
transistion metals....
Wasik Reply
Why study ecology
Amos Reply
What name is given to group 8metals on a periodic table
Amos
to know interaction of living organisms and their environment
Alice
what is evolution
Elia Reply
Is the gradual change of something it can be either organisms
Amos
which of the following statements about the moss life cycle is false?
Israel Reply
posterior lobe of pitutary contains what?
MR Reply
What if vincristine and colchicibe disrupt mitosis by binding to tubulin
Rohith Reply
A plant in the understory of a forest displays a segmented stem and slender leaves arranged in a whorl. It is probably....
Israel Reply
How did the development of a vascular system contribute to the increase in size of plants?
Israel
If a flower lacked a megasporangium and microsporangium, what type of gametes would not form?
Israel
Seed plants are.. A. all homosporous B. mostly homosporous with some heterosporous C. mostly heterosporous with some homosporous D. all heterosporous
Israel
Besides the seed, what other major structure diminishes a plant's reliance on water for reproduction?
Israel
what role did the adaptations of seed and pollen play in the development and expansion of seed plants?
Israel
Some cycads are considered endangered species and their trade is severely restricted. Customs officials stop suspected smugglers who claim that the plants in their possession are palm trees, not cycads. How would a botanist distinguish between the two types of plants?
Israel
What are the two structures that allow angiosperms to be the dominant form of plant life in most terrestrial ecosystems?
Israel
how are carbohydrates,proteins and fats formed from triose phosphate
fonyuy Reply
Why does the actin filament only move in one direction? Describe in great detail.
Lashonda Reply
Two events happen when calcium binds to troponin.
Lashonda

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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