1. CHAPTER 4: TISSUE 1
4 main types of tissues
1. Epithelial: Epithelium, sheets of cells that cover the exterior
surfaces of the body, lines internal cavities and passageways, and
forms certain glands.
2. Connective: binds the cells and organs of the body together and
functions in protection, support, and integration of all parts of the
body.
3. Muscle: excitable, responding to stimulation and contracting to
provide movement, and occurs as three major types: skeletal
(voluntary), smooth and cardiac muscle in the heart.
2. 4 Types of Tissues 2
4. Nervous: excitable, allowing the propagation of electrochemical
signals in the form of nerve impulses that communicate betwee3n
different regions of the body.
4. ORGAN 4
The next level of organization is the organ. This is where several types
of tissue come together to form a working unit.
Embryonic Origin of Tissues:
Zygote, fertilized egg. First embryonic cells generated have the ability
to differentiate into any type of cell in the body. Totipotent- each has
the capacity to divide, differentiate, and develop into a new organism.
As this cell proliferation continues, three major cell lineages are
established within the embryo. At the point each lineage forms the
distinct germ layers from which all of the tissues and organs of the
human body eventually will form.
5. Germ Layers 5
Each germ layer is identified by its relative position:
• Ectoderm: outer
• Mesoderm: middle (muscle tissue)
• Endoderm: inner (nervous tissue)
Epithelial tissue originates in all three
Layers.
6. Tissue Membranes 6
• Tissue membrane: thin layer or sheet of cells that covers the outside
of the body (ie. skin), the organs (pericardium), internal passageways
that lead to the exterior of the body (abdominal mesenteries), and
the lining of the moveable joint cavities. There are two basic types of
tissue membranes:
1. Connective tissue: formed solely by connective tissue.
Encapsulates organs, such as the kidneys, and line our movable
joints. Synovial membrane: type of connective tissue membrane
that lines the cavity of a freely movable joint. (shoulder, knee and
elbow). Synovial fluid is a natural lubricant allows for movement.
7. Tissue Membranes – continued 7
2. Epithelial membrane: composed of epithelium attached to a layer
of connective tissue. (skin). Mucous membrane a composite of
connective and epithelial tissues. Sometimes called mucosae,
these membranes line the body cavities and passageways that open
to the external environment and include digestive, respiratory,
excretory, and reproductive tracts. Mucous is produced by the
epithelial exocrine glands, covers the epithelial layer. The
underlying connective tissue is called lamina propria (own layer),
helps support the fragile epithelial layer.
8. Tissue membranes – continued 8
Serous membrane: epithelial membrane composed mesodermally derived
epithelium called the mesothelium, that is supported by the connective
tissue. These membranes those cavities that do not open to the outside, and
they cover organs located within those cavities. They are essentially
membranous bags, with mesothelium lining the inside and connective tissue
outside. Serous fluid secreted by the cells of the thin squamous
mesothelium lubricates the membrane, reduces abrasion and friction
between the organs. Serous membranes are identified according to location.
Three serous membranes line the thoracic cavity; two pleura that cover the
lungs and pericardium that covers the heart. The peritoneum is the serous
membrane in the abdominal cavity that covers abdominal organs and forms
double sheets of mesenteries that suspend many of the digestive organs.
9. Tissue membranes – continued 9
Skin is the epithelial membrane call the cutaneous membrane.
Stratified squamous epithelial membrane resting on top of connective
tissue. The apical surface of this membrane is exposed to the external
environment and is covered with dead, keratinized cells that help
protect the body from desiccation and pathogens.
11. Epithelial Tissue 11
Epithelial tissue: essentially large sheets of cells covering all the surfaces of
the body exposed to the outside world and lining the outside of organs.
Epithelium also forms much of the glandular tissue of the body. Other areas
exposed to the outside are airways, the digestive tract, as well as the urinary
and reproductive systems, all which are lined with epithelium. Hollow
organs and body cavities that do not connect to the exterior of the body,
which lines blood vessels and serous membranes, are lined by endothelium.
The epithelia lining the skin, parts of the mouth and nose and the anus
develops from the ectoderm. Cells lining the airways and most of the
digestive system originate in the endoderm. Epithelium that lines vessels in
the lymphatic and cardiovascular systems derives from the mesoderm and
called an endothelium.
12. Epithelial Tissue – continued 12
• Epithelial tissue are nearly completely avascular. No blood vessels cross
the basement membrane to enter the tissue and nutrients must come by
diffusion or absorption from underlying tissue or surface.
GENERALIZED FUNCTIONS:
• Provides the body’s first line of protection from physical, chemical and
biological wear and tear. Gatekeeper’s of the body controlling permeability
and allowing selective transfer of materials across a physical barrier. All
substances that enter the body must cross an epithelium. Many are
capable of secretion and release mucous and specific chemical compounds
onto their apical surfaces. Epithelium of the small intestines releases
digestive enzymes. Cells lining the respiratory tract secrete mucous.
14. Classification of Epithelial Tissues 14
• Classified according to the shape of the cells and number of the cell
layers format. Cell shapes: Squamous (flattened and thin), Cuboidal
(boxy, as wide as it is tall), Columnar (rectangular, taller than it is
wide).
• Simple epithelium: organized as a single layer of cells
• Stratified epithelial: formed by several layers of cells
• Pseudostratified: tissue with a single layer of irregularly shaped cells
that give the appearance of more than one layer.
15. Simple Epithelium 15
Simple squamous epithelium: appearance of thin scales. Places
where this type of tissue is found. Alveoli of the lungs where the gases
diffuse, segments of the kidney tubules, lining of capillaries and interior
of blood vessels.
Endothelium: epithelial tissue that lines vessels of the lymphatic and
cardiovascular system. Made up of a single layer of squamous cells.
Mesothelium: forms a surface layer of the serous membrane that lines
body cavities and internal organs. Primary function is to provide
smooth and protective surface. Secrete a fluid that lubricates the
mesothelium.
16. Simple Epithelium – continued 16
• Simple cuboidal epithelium: nucleus of the box-like cells appear
round and generally located near center of cell. Active in secretion
and absorption of molecules . Observed in the lining of the kidney
tubules and ducts of glands.
• Simple columnar epithelium: nucleus of the tall column-like cells
tend to enlongated and located in the basal end of the cell. Active in
absorption and secretion of molecules. Forms the lining of some
sections of the digestive system and parts of the female reproductive
tract. Ciliated columnar found in lining of the fallopian tubes and
parts of the respiratory system.
17. Simple Epithelium – continued 17
• Pseudostratified columnar: appears to stratified but consists of a
single layer of irregularly shaped and differently sized columnar cells.
Found in the respiratory tract where some of the cells have cilia.
18. Stratified Epithelium 18
• Stratified Epithelium: consists of several stacked layers of cells. Protects
against physical and chemical wear and tear.
• Stratified Squamous epithelium: most common type in the human body.
Top layer may be covered with dead cells filled with keratin. Example –
Mammalian skin.
• Stratified Cuboidal epithelium: function is protective tissue. Found in
sweat glands, salivary glands and mammary glands.
• Stratified columnar epithelium: Secretes and protects. Found in the male
urethra and the ducts of some glands.
• Transitional epithelium: only found in the urinary system, specifically in the
ureters and urinary bladder. Bladder empty, the epithelium is convoluted
and has cuboidal cells. Bladder fills with urine it loses its convolutions and
goes from cuboidal to squamous.
19. Stratified Epithelium: 19
• Simple cuboidal epithelium: active in secretion and absorptions of
molecule. Observed in the lining of the kidneys and in the ducts of
glands.
• Simple columnar epithelium: active in secretion and absorption of
molecules. Form the lining of some sections of the digestive systems
and parts of the female reproductive tract. Ciliated columnar
epithelium: contains cilia and is found in the lining of the fallopian
tubes and parts of the respiratory system. The cilia helps remove
particulate matter.
• Pseudostratified columnar epithelium: found in the respiratory tract,
where some cells have cilia.
21. Glandular Epithelium: 21
• A gland is a structure made up of one or more cells modified to
synthesize and secrete chemicals. Glands can be classified two ways.
Endocrine gland: ductless gland that releases secretions directly into
surrounding tissues and fluids. These secretions are called hormones.
Released through interstitial fluid, diffused into the bloodstream and
delivered to targets. Endocrine system part of the major regulatory
systems coordinating the regulation and integration of body
responses. Examples: anterior pituitary, thymus, adrenal cortex,
gonads.
22. Glandular Epithelium- continued 22
Exocrine gland: secretions leave through a duct that opens directly,
or indirectly to the external environment. Secretions that lead to the
epithelial surface. Mucous, sweat, saliva and breast milk are
examples. They are all discharged through tubular ducts.
• Glandular structure: Exocrine glands are either unicellular or
multicellular.
Unicellular are scattered single cells, such as goblet cells- mucous
secreting “gland” interspersed between columnar epithelial cells of
mucous membranes. These are found in the small and large
intestines.
23. Glandular Epithelium- continued 23
Multicellular exocrine glands: secretes directly into an inner cavity.
Line the internal cavities of the abdomen and chest and release
secretions directly into the cavities.
24. Methods and types of secretions: 24
• Merocrine secretion: most common type. Secretions enclosed in
vesicles where contents is released by exocytosis. Sweat – example
• Apocrine secretion: Sweat glands of the armpits. These types of
glands continue to secrete and produce contents with little damage
to the cells.
• Holocrine secretion: Sebaceous glands that produce oils on the skin
and hair. These types of glands rupture and destroy the entire gland
cell. It accumulates it secretion and releases only when it bursts.
26. Secretions 26
• Glands are also named after the products they produce. The serous
gland produces watery, blood-plasma-like secretions rich in enzymes
such as alpha amylase, whereas the mucous gland releases watery to
viscous products rich in the glycoprotein mucin. Both serous and
mucous glands are common in the salivary glands of the mouth.
Mixed exocrine glands contain both serous and mucous glands and
release both types of secretions.
27. Connective tissue 27
Functions of Connective Tissues:
• Support and connect other tissues (from the connective tissue sheath
that surrounds muscle cells, to tendons that attach muscles to bone
and the skeleton that supports the positions of the body.
• Protection: fibrous capsules and bones that protect delicate organs
and the skeletal system. Specialized cells defend the body from
microorganisms that enter the body. Blood and lymph transports
fluid, nutrients, waste and chemical messengers. Adipose cells store
surplus energy in the form of fat and contributes to the thermal
insulation of the body.
28. Embryonic Connective tissue 28
• The mesodermal layer of the embryo is where all connective tissue
derives. Mesenchyme – stem cell line from which connective tissues
are later derived. Mucous connective tissue (Wharton’s jelly) –
embryonic connective tissue forms in the umbilical cord. This tissue is
no longer present after birth.
29. Classification of Connective tissue: 29
• Connective tissue proper includes loose connective tissue and dense
connective tissue. Both tissues have a variety of cell types and
protein fibers suspended in a viscous ground substance. Dense
connective tissue is reinforced by bundles of fibers that provide
tensile strength, elasticity, and protection. In loose connective tissue,
the fibers are loosely organized, leaving large spaces in between.
• Supportive connective tissue—bone and cartilage—provide structure
and strength to the body and protect soft tissues.
• In fluid connective tissue - lymph and blood, various specialized cells
circulate in a watery fluid containing salts, nutrients, and dissolved
proteins.
31. Connective Tissue Proper 31
• Fibroblasts – present in all connective tissue. Most abundant cell
found in connective tissue proper.
• Fibrocyte – less active form of fibroblasts, second most abundant cell
type of connective tissue proper.
• Adipocytes – store lipids as droplets that fill most of the cytoplasm.
Two types: white and brown. Brown adipocytes – store lipids as
many droplets and have high metabolic activity. White adipocytes –
store lipids in a single large drop and metabolically less active.
Effective in storing large amounts of fat as seen in obese individuals.
• Mesenchymal cell – multipotent adult stem cell. Needed for repair
and healing of damaged tissue.
32. Connective Tissue Proper – continued 32
• Macrophage – large cell derive from monocyte. Essential component
of the immune system.
• Mast cells – has many cytoplasmic granules. Histamine is produced
when a mast cell reacts to an irritation(inflammatory mediator, which
causes vasodilation and increased blood flow at the site of injury or
infection and heparin. Part of the immune system.
33. Connective Tissue Fibers 33
Three main types of fiber secreted by fibroblasts:
Collagen fiber: flexible, have great tensile strength, resist stretching,
and give ligaments and tendons their characteristic resilience and
strength.
Elastic fiber: after being stretched or compressed, it will return to its
original shape. Elastic tissues found in skin. Elastic ligaments of the
vertebral column.
Reticular fiber: found throughout the body, but most abundant in
the reticular tissue of the soft organs, liver and spleen.
34. Loose Connective Tissue: 34
Found between many organs where it acts both to absorb shock and
bind tissues together. It allows water, salt, and various nutrients to
diffuse through to adjacent or imbedded cells and tissues.
oAdipose tissue: consists mostly of fat storage cells. White adipose
tissue - most abundant and contributes mostly to lipid storage and be
serve as an insulation from cold temperature and mechanical injuries.
It can be found protecting kidneys and cushioning the back of the eye.
Brown adipose tissue – more common in infants, baby fat. Reduced
amount in adults, found mainly in the neck and clavicular regions of
the body. Thermogenic.
35. Loose Connective Tissue – continued: 35
oAreolar tissue – fills in spaces between muscle fibers, surrounds
blood and lymph vessels, supports organs in the abdominal cavity.
oReticular tissue – mesh-like supportive framework for soft organs,
lymphatic tissue, spleen and liver.
36. Dense Connective Tissue 36
Contains more collagen fibers than loose connective tissue. Displays a
greater resistance to stretching. Two major categories:
Dense Regular: fibers are parallel to each other, enhances tensile strength
and resistance to stretching in direction of fiber orientation. Makes up
ligaments and tendons. In ligaments – not all fibers are parallel. Dense
regular elastic tissue – allows the ligament to return to its original length
after stretching. Ligaments in the vocal folds and between the vertebrae
are elastic.
Dense Irregular: direction of fiber is random. Gives the tissue greater
strength in all directions and less strength in one particular direction.
Example: dermis of the skin (dense irregular connective tissue). Strength
of arterial walls and ability to regain original shape after stretching. (Dense
irregular elastic tissue.
37. Supportive connective tissue: 37
Two major forms that allow the body to maintain its posture and
protect internal organs. Cartilage and Bone.
Cartilage: Chondrocytes- cartilage cells. Cartilaginous tissue is
avascular, all nutrients need to diffuse through the matrix to reach
the chondrocytes. This makes for a very slow healing of cartilaginous
tissue.
38. Cartilage tissue 38
Three types of cartilage tissue:
1) Hyaline cartilage: most common type in the body. Found in the rib
cage and nose, covers bones where they meet to form movable
joints. Allows for continued growth until adulthood.
2) Fibrocartilage: tough. Located in the knee and jaw joints and the
intervertebral discs.
3) Elastic cartilage: gives rigid support as well as elasticity. Tug at your
ear lobes and notice they return to their initial shape. External ear
contains elastic cartilage.
39. Supportive connective tissue – continued 39
Two major forms that allow the body to maintain its posture and
protect internal organs. Cartilage and Bone.
Bone: hardest connective tissue. Provides protection to internal
organs, supports the body. Osteocytes are located in the lacunae and
are the main cells of the bone. Bone is highly vascularized. This type
of tissue can recover in a relatively short times from an injury.
Cancellous bone: looks like a sponge under the microscope. Lighter
than compact bone (solid and has greater structural strength). Found
in the interior of some bones and at the ends of long bones.
40. Fluid connective tissue 40
Blood and lymph are fluid connective tissues.
• Erythrocytes: red blood cells (RBCs) transports oxygen and some
carbon dioxide.
• Leukocytes: White blood cells (WBCs) defends against potentially
harmful microorganisms or molecules.
• Platelets: cell fragments involved in blood clotting.
41. Muscle Tissue and motion 41
Characterized by properties that allow movement. Excitable, respond to a
stimulus. Contractile, can shorten and generate a pulling force. Bones –
causes contractions of muscles causes bone to move. Some movement is
voluntary (under conscious control) or involuntary (not under conscious
control).
Classified into three types according to structure and function:
1. Skeletal: attached to bone. Makes possible locomotion, facial
expressions, posture and other voluntary movements of the body. 40%
of body mass made up of skeletal muscle. Can generate body heat by
contraction and participates in thermal homeostasis. Involuntary
movement of shivering. Striations, cylindrical cells and multiple nuclei
are observed in skeletal muscle. Mitochondria are the hard working
cells found in abundance in this type of muscle.
42. Classified into three types according to
structure and function – continued 42
2. Cardiac: forms the contractile walls of the heart.
3. Smooth: this type of tissue contracts involuntary for movements in
internal organs. Digestive, urinary, and reproductive systems as
well as arteries and airways.
Tissue Histology Function Location
Skeletal
Long cylindrical fiber,
striated, many
peripherally located
nuclei
Voluntary movement, produces heat, protects
organs
Attached to bones and
around entrance points to
body (e.g., mouth, anus)
Cardiac
Short, branched,
striated, single central
nucleus
Contracts to pump blood Heart
Smooth
Short, spindle-shaped,
no evident striation,
single nucleus in each
fiber
Involuntary movement, moves food, involuntary
control of respiration, moves secretions,
regulates flow of blood in arteries by contraction
Walls of major organs and
passageways
43. Nervous Tissue 43
Characterized by being excitable and capable of sending and receiving
electrochemical signals that provide the body with information.
Two main classes of cells make up nervous tissue: the neuron and
neuroglia.
1. Neurons: propagate information via electrochemical impulses,
called action potentials, which are biochemically linked to the
release of chemical signals. Responsible for the transmission of the
nerve impulse.
45. Neuron 45
Three main parts:
Cell body: includes most of the cytoplasm, the organelles and the
nucleus.
Dendrites: branch off the cell body and appear as thin extensions.
Axon: long “tail” extends from the neuron body and can be wrapped
in an insulating layer known as the myelin (formed by accessory cells).
Synapse: gap between nerve cells, or between a nerve cell and its
target (muscle or gland)
46. Neuroglia or Glial Cells: 46
Classified as having a simple support role.
Astrocyte: named for their distinctive star shape.
Oligodendrocyte: produce myelin in the brain and spinal cord.
Schwann: produces myelin in the peripheral nervous system.
47. Tissue Injury 47
Inflammation is the standard, initial response of the body to injury. It
limits the extent of injury, partially or fully eliminates the cause of
injury, and initiate repair and regeneration of damaged tissues.
Necrosis or accidental cell death causes inflammation.
Acute inflammation resolves over time by healing the tissue.
Inflammation persisting becomes chronic and leads to diseased
conditions. Arthritis and tuberculosis are examples.
4 cardinal signs of inflammation: Redness, swelling, pain and local
heat. Loss of function may also be a sign.
48. Aging 48
The skin and other tissues become thinner and drier, reducing the elasticity,
contributing to wrinkles and high blood pressure. Gray hair and so on and so
forth. Joints stiffen due to loss of cartilage.
Incidence of heart diseases, respiratory syndromes and type 2 diabetes
increases with age. Wound healing is slower accompanied by a higher
frequency of infection due to the immune system declining.
When you begin to use your muscles, they can atrophy which is a loss of
mass.
The progressive impact of aging on the body varies considerably among
individuals, but studies indicate that exercise and healthy lifestyle choices
can slow down the deterioration of the body that comes with old. So to try
and slow the rate of aging, one must modify stress, exercise and diet.
