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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

prove starch in a mango leaf
Ruth Reply
prove starch in a leaf
Ruth
Identify the caste of termites or Honey bees
Mensah Reply
what is biology
Jackson Reply
biology is a study of living organism
Brilliant
what is the myelin sheath?
description on how an enzyme such as pepsin breaks down a substrate
linister Reply
what is biology
Kanzy Reply
study of life
Tufail
the study of life..meaning studying all aspects of life in humans,animals and everything inside the global
Nalukui
study of life
Memory
is the branch of science which deal with the study of living and non living things
David
draw the taxonomic hierarchy of classification
KC Reply
explain the following bush burning, deforestation, over grazing
Thomas Reply
what is biodiversity
Tracy
No idea
nana
Please what are alleles
nana
Deforestation: this is the cutting down of trees without planting new ones
Brilliant
over grazing is the continuously planting of crops in one particular land.
Friday
what is afforestation
Friday
what is physiology
Joseph Reply
the study of physical things
Nalukui
dealing with those things which you can see by your neck eyes
Odwa
Further explanation please
nana
the study of things tt interact with time,energy
David
can a lactating mother get pregnant
Elias Reply
what is cell
Deng Reply
the basic building blocks of all living matter...
Izzati
cell is a basic unit of life
MAI
building blocks ie cells not a cell there4 a cell is the basic unit of biotic things
David
Cell is a basic unit of life
Malekhotla
what's microscope
Emmanuel Reply
is any instrument that use to wiew or to see the small object that you can't see with our naked eye
MR
is any instrument used to magnifie small object
Memory
what is the function of the spinal cord
Gaone Reply
A cell is the structural and fictional unit of life
Evelyn Reply
what is tidal volume
Erick
tidal volume is the volume of each breath measured during inspiration or expiration or averged for the entire respiratory cycle
Gaone
Give function of the long strands of slippery or jelly like substance in eggs of the amphibians in water ?
Erick
the long strands of slippery or jelly like substance him eggs of amphibians in water helps in keeping the eggs moist and protection from predators
Gaone
sorry not him in
Gaone
what's is microscope
Emmanuel
How do bacteria useful?
Bisirikirwa
how can plant feed other animals
Nana Reply
After the animals has death and decayed then the plant used the nutrients to manufacture there food.
Yusuf
Plants and animals depends on each other. Meaning, plants help animals with greens and fruits or vegetables while animals provides nutrients when dead and decayed. Therefore,as you see the food web and food chain, you'll have more.
Jairenaririko

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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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