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Chapter 5
Tissues
Tissue Types
Cells are the building blocks of tissues
The human body has four tissue types:
– Epithelial
– Connective
– Muscular
– Nervous
Epithelial Tissue
Epithelial tissue
• covers the body
• lines all cavities
• composes the glands
It has neither blood vessels nor any extracellular substances between the
cells
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Epithelial Tissue
Epithelial types are identified by both the number of cell layers and the shape
of the cells in the upper layer
There are eight basic types of epithelium
– six identified by both the number of cells and their shape
– two named for the type of cell found in them
• transitional
• pseudostratifed
Epithelial cells can be flattened, cube-like, or columnar
Each shape mirrors the function of the tissue
Epithelial Tissue
Epithelial Tissue
Flattened cells, reminiscent of fried eggs, are called squamous cells
– squamous epithelium is thin enough to form a membrane through which
compounds can move via diffusion
Cuboidal and columnar epithelia are plumper and usually compose mucous
membranes
Simple epithelium has one layer of cells and usually functions as a diffusion or
absorption membrane
– the lining blood vessels
– the lining of respiratory membranes
Stratified epithelia have many layers of cells and are designed for protection
– outer layer of skin
– salivary gland ducts
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Epithelial Tissue
Glands are composed of epithelial tissue
Glands are classified by how their secretions are released
– glands that secrete into ducts are exocrine glands
• salivary glands, sweat glands
– endocrine glands have no ducts, they secrete directly into the surrounding
extracellular fluid
• endocrine glands secrete hormones that are then picked up by the bloodstream
and carried throughout the body
• Adrenal glands, thyroid glands, pituitary glands
Connective Tissue
Connective tissue connects the structures of the body
•
•
it binds, supports, and anchors the body
It is the most abundant type of tissue in the body
Soft connective tissue examples include parts of our skin, tendons, and blood
vessels
– it has a matrix composed of semi-fluid substance
– it has fibroblasts that secrete fibers, and white blood cells that fight infection
Connective Tissue
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Connective Tissue
Connective Tissue
Connective Tissue
Connective tissue is composed of cells suspended in a noncellular matrix
The matrix, or “ground substance,” is secreted by the connective tissue cells
•
•
the matrix determines the characteristics of the connective tissue
it contains fibers of collagen (for strength) and elastin (for flexibility, stretch,
and recoil)
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Connective Tissue
Cartilage, bone, blood, and lymph are types of specialized connective tissues
Cartilage is a unique connective tissue because it is avascular
– other types of connective tissue all have rich blood supplies
Chondrocytes, the cartilaginous cells, secrete a gel-like matrix that eventually
surrounds and imprisons them, segregating them from direct contact with
one another or any nutrient supply
Cartilage heals slowly because nutrients must diffuse through the matrix to
the chondrocytes
– nutrients cannot reach the cells directly via the bloodstream
– osteoarthritis is difficult to treat because cartilage is avascular and therefore
does not respond quickly to medications
Connective Tissue
Connective Tissue
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Connective Tissue
Connective Tissue
The most common type of cartilage is hyaline cartilage
Hyaline cartilage covers the ends of bones, allowing them to slide against one
another without damage
– it is also found in your nose
During development, the entire skeleton is modeled in hyaline cartilage, which
then ossifies
A second kind of cartilage is elastic cartilage
– elastic cartilage comprises the outer ear and the epiglottis
The fibrocartilage matrix is packed with collagen fibers
– it is found where extra strength is needed
– it cushions knee joints and the disks between the vertebrae
Connective Tissue
Blood and lymph are considered fluid connective tissues because their matrix
is not a solid
Blood is composed of specialized cells that are carried in the fluid matrix, or
plasma
– blood’s main function is to transport nutrients, gases, hormones, and wastes
Lymph is derived from the interstitial fluid that bathes the cells
– It is collected in the lymphatic vessels
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Bone
Bone is a hard mineralized tissue found in the skeleton
Bone cells secrete an osteoid substance that eventually hardens and
surrounds the cells in an ossified matrix.
– this “osteoid ground substance” includes proteins, water, calcium, and phosphorous
salts
– once the matrix ossifies, the cells remain in contact with one another through small
channels called canaliculi
Adipose Tissue
Adipose tissue contains cells that are specialized for lipid storage (fat cells)
Adipose tissue does not have an extensive extracellular matrix
Cellulite “bumps” on the skin indicate where the adipose matrix is connected
to the skin
– adipose cells within the fibrous matrix can expand with the swelling of the fat droplets
they contain, while the matrix fibers cannot stretch as far.
– different stretching capacities of these two components of adipose tissue form dimples
on the skin
Muscular Tissue
Muscular tissue provides movement and heat
The function of muscular tissue is to contract
–
cells get shorter, generating force and often movement
There are three types of muscular tissue are
•
•
•
skeletal muscle
smooth muscle
cardiac muscle.
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Muscular Tissue
Muscular Tissue
Muscular Tissue
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Skeletal Muscle
Skeletal muscle is the tissue that makes up the muscles
– it is highly organized, with cells lying parallel to each other
– skeletal muscle moves limbs and stabilizes our trunk
Smooth Muscle
Smooth muscle lines hollow organs such as the blood vessels and the
digestive tract
– Smooth muscle cells are short, cylindrical cells that taper at both ends and have only
one nucleus
– They are not striated, and are not under voluntary control
Cardiac Muscle
Cardiac (heart) muscle has short, branched, striated cells, with one nucleus at
the center of each cell
Specialized communication junctions called intercalated discs facilitate the
heartbeat by transmitting the signal to contract
Intercalated discs are gap junctions where the closely knit cell membranes
help to spread the contraction impulse while also binding the cells
together
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Nervous Tissue
Nervous tissue responds to the environment by detecting, processing, and
coordinating information
Nervous tissue contains two categories of cells: neurons and neuroglia
– Neuroglia are the supporting cells of nervous tissue (“glia” means
“glue”)
• they improve nutrient flow to the neurons, provide physical
support, remove debris, and provide electrical insulation
Nervous Tissue
Nervous Tissue
Nerves are clusters of neurons and their projections, sheathed in connective
tissue
– nerves exist in the body's periphery, and are therefore a part of the peripheral
nervous system
Sensory nerves conduct sensory messages from the body's sensory organs to
the spinal cord, which routes the information to the brain
Motor nerves carry impulses that cause muscular movement or glandular
secretion from the spinal cord to the muscles and glands
The brain and spinal cord contain neurons that receive and integrate
information and stimulate motor neurons to fire
– these information-processing neurons occur in the central axis of the body, so
they comprise the central nervous system
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Cellular Organization
•
Cellular organization or hierarchy, is visible in all life forms
– Atom
– Molecule
– Organelle
– Cell
– Tissue
– Organ
– Organ system
– Organism
Organ Systems
There are 11 organ systems in the human body
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–
–
–
–
–
–
–
–
–
–
integumentary - protecting and covering
skeletal - support
muscular - movement and heat production
nervous - sensing and responding
cardiovascular - transporting fluids and oxygen
respiratory - gas exchange
urinary - fluid balance
endocrine - regulating sequential growth and development
digestive - obtaining nutrients
lymphatic - immunity
reproductive systems - continuation of species
Ten of these systems help maintain homeostasis, while the reproductive
system maintains the human population
Organ Systems
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Organ Systems
Organ Systems
Organ Systems
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Organ Systems
Anatomical Position
Used as a standard, anatomical position allows us to make sense of
directional terms
Body Cavities
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Body Cavities
The body has two large cavities, the ventral and dorsal cavities
The thoracic cavity includes the chest area and houses the heart,
lungs, vessels, and lymphatic system
The “guts” are found within the abdominal cavity, which is lined with
peritoneum
The organs of the urinary system and the reproductive system are
located in the pelvic cavity.
The dorsal body cavity includes the cranial cavity housing the brain,
and the vertebral cavity which contains the spinal cord
The integumentary system:
•
Includes the skin and accessory organs such as hair,
nails and gland
•
The skin has two main regions called the epidermis
and the dermis
•
Under the skin there is a subcutaneous layer
between the dermis and internal structures where
fat is stored
•
Is important for maintaining homeostasis
What are the functions of the
integumentary system
1. Protects the body from physical trauma, invasion
by pathogens and water loss
2. Helps regulate body temperature
3. Allows us to be aware of our surroundings through
sensory receptors
4. Synthesizes chemicals such as melanin and vitamin
D
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There are two regions of the skin
•
•
Epidermis
Dermis
The epidermis:
•
•
•
The thin, outermost layer of the skin
Made of epithelial tissue
Cells in the uppermost cells are dead and become
filled with keratin thus acting as a waterproof
barrier
Langerhans cells are a type of white blood cell that
help fight pathogens
Melanocytes produce melanin that lend to skin
color and protection for UV light
Some cells convert cholesterol to vitamin D
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What you need to know about skin
cancer?
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2 of the 3 types that arise in the epidermis:
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Basal cell carcinoma is the most common yet least deadly form of
skin cancer
Melanoma is the most deadly form of skin cancer but is the least
common
What can you do to help prevent this?
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•
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Stay out of the sun between 10am-3pm
Wear protective clothing (tight weave, treated sunglasses, widebrimmed hat)
Use sunscreen with an SPF of at least 15 and protects from UV-A
and UV-B rays
Don’t use tanning beds
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What might skin cancer look like?
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