Tissues and
Membranes
Tissues…
• The human body consists of trillion of cells,
but they do not work independently
• The cell must work together to perform
various tasks to keep the body in
homeostasis
• In order for cells to work together, they form
tissues
• To help study the various cells and the
tissues they make, anatomists have
subdivided the tissues into four major groups
and those groups are further subdivided
according to their cellular makeup
General Information…
• Some tissues, such as epithelial, connective, muscle or
nervous, may or may not have surface modifications
• Microvilli – contain microtubules which help increase the surface
area of the cell
• Cilia – contain microfilaments which help move materials along
the outer surface of the cell
• Cell junctions attach the cells of the tissues together forming
an excellent barrier
• Three types of cell junctions
1. Tight junction – prevents movement of materials between cells
and are usually found in epithelial cells
2. Adhering junction – holds the cells together and are found in
skin and cardiac tissue
3. Gap junction
Three Types of Cell Junctions
1. Tight junction – prevents movement of materials
between cells and are usually found in epithelial cells
2. Adhering junction – holds the cells together and are
found in skin and cardiac tissue
• Desmosomes – the junction is a “spot” between the
cells
• Intermediate junctions – the junction appears as a
“band” around the cells
3. Gap junction – transmits impulse and small ions
from cell to cell and are found in heart, smooth, and
some nerve cells
The Four Tissue Groups…
Tissue Type
Characteristic
Epithelial
(cover)
Consists of cells that make
up the inside or outside
lining of organs
Consists of cells that have
Muscular
the ability to contract and
(movement) relax
Neural
(control)
Connective
(support)
Consists of cells that
conduct impulses or cells
that protect the nervous
system
Type of cell within the
tissues
Squamous, cuboidal,
columnar
Skeletal muscle,
smooth muscle, cardiac
muscle
Neuron, glial
Consists of cells that have a Adipose, areolar, blood,
matrix and typically fill
bone, cartilage, dense,
internal spaces within the
reticular
body
Epithelia Characteristics…
• The cells fit closely together to form continuous sheets
• They are bound together at many points called cell
junctions
• They always have one free surface called the apical
surface, which is exposed to the body’s exterior or to
the cavity of an internal organ it is lining
Epithelia Characteristics
con’t…
• They rest on a basement membrane, which is a
structureless material secreted by the cells
• They have no blood supply (avascular), therefore they
depend on diffusion from capillaries under connective
tissue for food and oxygen
• When well nourished, they can regenerate
Classification of Epithelia…
•
Epithelia are classified according to:
1.
Cell arrangement



2.
Simple – one layer of cells
Stratified – two or more layers of cells
All attached to a “basement” membrane
Shape


If the cells are stratified, the free surface determines
the name
There are four main types
i.
ii.
iii.
iv.
Squamous
Cuboidal
Columnar
pseudostratified
Drawing Tissue…
• Draw each of the different types of tissue
Bell Ringer…
• What makes tissue?
• What are the 4 types of tissue and what is each of their
main functions?
• Draw a simple squamous epithelial tissue – label the
basement membrane, the apical surface, and cell
junctions
The cells of Epithelial
Tissue…
• Squamous cells
Flat and irregular in appearance
Found in the lining of the skin
Our first line of defense
• Cuboidal cells
Shaped like little squares
Found in the lining of the urinary tubes
Secrete and absorb material
The cells of Epithelial Tissue
con’t…
•
•
Columnar cells
 Shaped like columns
 Found in the lining of the trachea
 Secrete and absorb material
Glandular cells
 Obtain needed materials from the blood and use
them to make their secretion, which they discharge
 Two types of glands develop from epithelial sheets
i. Endocrine glands
ii. Exocrine glands
The cells of Muscular
Tissue…
• Skeletal muscle cells
Are elongated cells with striations
Found making up the muscles associated with the
skeletal system
Contract and relax under voluntary control
• Smooth muscle cells
Are elongated cells without striations
Found making up the uterus and blood vessels
Contract and relax under involuntary control
The cells of Muscular Tissue
con’t…
• Cardiac muscle cells
Consists of intercalated discs
Found making up only the heart
Contract and relax in a non-voluntary pulsating manner
The cells of Neural Tissue…
• Neurons make up neural tissue
Consists of dendrites, soma and an axon
Found making up the nervous system such as the
brain and spinal cord
Conduct impulses
Glial cells
Have a variety of shapes and sizes
Found either nearby or surrounding the neurons
Provide protection for neurons
Connective Tissue
• Connective tissue represents the most diverse tissue
group of the human body
• Even though cells are quite different from each other,
they do have some commonality, which is they all have
matrix of some sort
• The matrix is the material that surrounds the cells
The Major Matrix Types…
•
There are 4 major matrix materials
a.
b.
c.
d.
Fiber – the fibers of the matrix can be long, slender fibers
or short, thick fibers
Liquid – liquids such as plasma
Solid – creates a tough, strong type of tissue
Gel – creates a tough but yet very flexible type of tissue
Bell Ringer…
Identify each type of tissue and explain why you choose it
Bell ringer…
• What is the one common thing that all connective tissue
has in common?
• What type of cells protect nerve tissue?
The cells of Connective Tissue…
• Adipose cells
Are round and appear empty, but they are full of
fat
Found surrounding various organs of the body
Provide insulation
Have a fiber matrix
• Areolar cells
Are small and have long, thin fibers running
between them making up the matrix
Found between our skin and muscle and provide
attachment of our skin to the muscle
The cells of Connective Tissue
con’t…
• Blood cells
Are small anucleated with a plasma matrix
Can be found in our circulatory system
Transport oxygen and carbon dioxide to and from
other cells in the body
• Dense cells
Are parallel fibers in a fiber matrix
Make up tendons and ligaments
Tendons provide attachment of muscles to bone
Ligaments provide attachment of one bone to
another
The cells of Connective Tissue
con’t…
• Bone cell
Form concentric rings around a central canal
Can be found in our bones
Provide strength
In a solid matrix made of calcium phosphate
• Cartilage cell
Are small and sit in a rather large lacuna
Can be found within our joints
Have a gel matrix, which allows for flexibility
The cells of Connective Tissue
con’t…
• Reticular cell
Are small and have short, thick fibers running between them
Can be found making up the framework of the liver, spleen,
tonsils, appendix, and thymus gland
Have a fiber matrix that consists of short, thick fibers
Glandular tissue…
• Consists of one or more cells that make AND secrete a
particular product called a secretion
• The secretion typically contains protein molecules in an
aqueous fluid
2 Major Types of Glands
1.
Endocrine glands



2.
Do not have ducts (ductless)
Their secretions (all hormones) diffuse directly into the
blood vessels found with in the gland
Ex – thyroid, adrenal, pituitary
Exocrine glands


Have ducts in which their secretions empty through to get to
the epithelial surface
Ex – sweat, oil, liver and pancreas (can be both internal and
external)
Cartilage types…
1. Hyaline cartilage
 Most widespread type
 Supporting structures of the larynx, voice box,
attaches the ribs to the sternum
 Covers the ends of bones where they form
joints
2. Elastic cartilage
 Found where a structure with elasticity is
desired – external ear
3. Fibrocartilage
 Forms the cushion-like discs between the
vertebrae of the spinal cord
Body Membranes…
•
There are 4 major types of membranes in the body
a.
b.
c.
d.
Cutaneous membranes
Mucous membranes
Serous membranes
Synovial membranes
Cutaneous membrane…
• The cutaneous membrane is actually the skin
• It covers the entire body and is made up of squamous
epithelial cells
Mucous membranes…
• Typically consist of columnar epithelial cells
• Produce a mucus, which provides protection
to the tissue they line, such as the cavities
that open to the outside of the body
The digestive tract – opens via the mouth and
anus
The respiratory tract – opens to the outside via
the mouth and nose
The reproductive tract – opens to the outside via
the vaginal opening
The urinary tract – open to the outside via the
urethral opening
Serous membranes…
• Produce serous fluid, which provides
protection for the tissue they cover
• Are made of epithelial cells that are
supported by connective tissue
• Line internal cavities of the body that are not
open to the outside
The pleural membranes – cover the lungs
The peritoneal membranes – cover organs such
as the stomach and liver
The pericardial membrane – covers the heart
Synovial membranes
•
•
•
•
Produce synovial fluid
This fluid helps to reduce abrasion at the joint site
They are made of connective tissue
They line the joints of the body
Tissue Injury…
• The body has many techniques for protecting itself from
uninvited guests or injury at the tissue level:
 Intact physical barriers (skin and mucous membranes)
 Cilia
 Strong acid produced by glands in the stomach lining
Tissue injury…
• When tissue injury does occur, it stimulates both the
body’s inflammatory and immune responses
 Inflammatory – a non-specific response that attempts to
prevent further injury
 Immune response – extremely specific and attacks
recognized invaders – bacteria, viruses, toxins
Tissue Repair…
•
•
a.k.a wound healing
Occurs in two major ways:
1.
2.
Regeneration- the replacement of destroyed cells by the
same kind of cells
Fibrosis – repair involves dense connective tissue, which
forms scar tissue
Determining the type of
repair…
•
The type of repair that occurs depends on:
1.
2.
•
The type of tissue damaged
The severity of the injury
In general, incisions heal much more successfully than
lacerations:


Incision – a clean cut
Laceration – ragged tear
Steps in tissue repair…
1. The broken blood vessels bleed, causing
inflammatory chemicals to be released
2. The local blood vessels dilate and become
more permeable, allowing white blood
cells, fluid and plasma/clotting proteins to
enter the injured area
3. The clotting proteins construct a clot, which
stops the loss of blood and holds the
wound together preventing harmful
bacteria from spreading to surrounding
tissue
Steps…
4. The surface dries and forms a scab
5. Granulation tissue forms
 It is a pink delicate tissue composed mainly of
capillary buds that grow into the damaged area
from the undamaged blood vessels
 The capillaries are fragile and bleed easily (pick
a scab – what happens)
 Contains phagocytes the eventually dispose of
the blood clot and fibroblast that synthesis
collagen fibers (scar tissue) to permanently
bridge the gap
Steps…
6.
7.
The surface epithelium begins to regenerate and
makes its way across the granulation tissue just
beneath the scab, which will then soon detach
The final result is a fully regenerated surface
epithelium that covers an underlying area of fibrosis
(the scar)

The scar is either visible or invisible depending on the
severity of the wound
Each type of tissue is
different…
• Epithelial tissue – skin tissue and mucous membranes –
regenerate beautifully
• Most fibrous connective tissue and bone tissue also
regenerate well
• Skeletal muscle regenerates poorly, if at all
• Cardiac muscle and nervous tissue within the brain and
spinal cord are only replaced by scar tissue
Why scar tissue is not beneficial…
• Scar tissue is strong, but is not as flexible as most
normal tissue
• It also does not have the ability to perform the normal
functions of the tissue it replaces
• This is why when scar tissue forms on any organ, it
usually hampers the function of that organ
Developmental Aspects of Cells
and Tissues…
• Growth through cell division (mitosis) occurs through
puberty – why we grow
• Cells/tissue exposed to fiction (epithelium) replace
lost cells throughout our lives
• Connective tissues remain mitotic and forms repair
(scar) tissue
• Muscle tissue becomes amitotic by the end of
puberty
• Nervous tissue becomes amitotic shortly after birth
Amitotic tissues are severely handicapped by injury
Developmental aspects
continued…
• Neoplasms, both benign and malignant,
represent abnormal cell masses in which
normal controls on cell division are not
working
• Hyperplasia is the increase in size of tissues
or organs that occurs when a tissue is
strongly stimulated or irritated
• Atrophy is the decrease in size of tissues or
organs that occurs when the organ is no
longer stimulated normally