Transcript Document

Hierarchy of
– Atoms
– Molecules
– Cells
– Tissues
– Organs
– Organ systems
– Organism
Tissues are the fundamental units of organs
and organ systems.
Tissues are the fundamental units of organs
and organ systems.
Tissues are the fundamental units of organs
and organ systems.
Tissues are the fundamental units of organs
and organ systems.
Loose connective tissue
• Histology is the study of tissues.
• A tissue is a group of cells and intercellular
materials that have a similar developmental origin,
structure, and function.
What you should know about a tissue
• Know the structure and be able to identify
it from a slide.
• Know the function.
• Know location in the body it is likely to be
• Know any special attributes of that tissue.
How to start identifying a tissue image.
Identify where the lumen (space)
is in the image if you can.
Identify where the basement
membrane is in the image is you
can. The basement membrane is
where the tissue stops.
Look at how many layers of cells
there are. (1)
Look at the shape of the cells
closest to the lumen. (long)
Look for other special features of
the tissue.
Give the tissue a complete name.
Image from:
An important thing to remember when
looking under the microscope
• To prepare tissue slides, scientists must
slice through the tissue. They can slice in
different ways.
Cross section
Longitudinal section
There are four basic tissue types.
Epithelial Tissue (Epithelium)
– functions include protection, absorption, filtration, and secretion.
Connective Tissue
– functions include protecting, supporting, binding together tissues, separating,
storing energy, transporting materials.
Muscle Tissue
– functions in the movement of the skeleton, pumping of the heart and the
movement of food.
Nervous Tissue
– send electrical signals through the body, thus forming a communication
system through the body.
Characteristics of the epithelium
• Cells fit closely together to form continuous sheets and are
bound together at many points by cell junctions.
• Cells have one free surface or edge. This apical surface is
exposed to the body’s exterior or to a cavity (the lumen)
• The lower cell surface rests on a basement membrane, a
structureless material secreted by the cells.
• These tissues are avascular, meaning that they have no
blood supply and depend on diffusion from capillaries in
the underlying connective tissue
• If well nourished, they can regenerate easily.
Characteristics of the epithelium
apical surface
of cells near
Image from:
Characteristics of the epithelium
Number of Layers:
Simple – single layer
Stratified – multiple-layered
Pseudostratified – only
appears to be multi-layered
Characteristics of the epithelium
Cell Shape:
Types of Epithelium
1. Simple Squamous Epithelium
2. Stratified Squamous Epithelium
3. Simple Cuboidal Epithelium
4. Stratified Cuboidal Epithelium
5. Simple Columnar Epithelium
6. Stratified Columnar Epithelium
7. Pseudostratified Columnar Epithelium
8. Transitional Epithelium
Epithelium is found everywhere.
Simple squamous
Epithelium lines
alveoli in lungs.
Simple cuboidal
Forms tubes in
Simple columnar
Epithelium lines
the intestine.
Epithelium lines
the esophagus.
Simple squamous epithelium
• Thin and leaky
• Good for exchange of materials by
– Blood vessels
– Alveoli
Simple squamous epithelium
These are the same tissue. Why do they look so different?
Images from:
Stratified squamous epithelium
• Regenerates rapidly by division of cells at
its attached surface
• New cells move toward the free surface;
older cells slough off
• Suited for covering and lining surfaces
subject to abrasion
• 2 types – nonkeratinized and keratinized
– keratin is a strong, fibrous protein
Stratified squamous epithelium
Images from:
Mouth, throat, esophagus, urethra, skin (keratinized)
Cuboidal epithelium
• Simple Cuboidal epithelium
– Secretion, absorption, protection
– Ducts of many glands, covering of ovary,
form kidney tubules
• Stratified Cuboidal epithelium
– Secretion, absorption
– Lines ducts of sweat glands.
Cuboidal epithelium
Kidney section
Images from:
Kidney tubules, glands, lining of terminal bronchioles, etc.
Sweat gland ducts, salivary gland ducts, etc.
Simple columnar epithelium
• Transportation, absorption, secretion,
• Large surface area
• Lines much of the digestive tract, gall bladder, and
large ducts of glands
• May have a brush border of microvilli
• May be ciliated – uterus, small bronchi, and
paranasal sinuses.
Simple columnar epithelium
Brush border
Images from:
Goblet Cell
Glands, bronchioles, stomach, intestines, bile ducts, etc.
Stratified columnar epithelium
• Surface cells are columnar
• Secretion, absorption, protection
• Some large excretory ducts, portions of the
male urethra
• No cilia
• Not common
Mammary gland ducts, larynx, urethra (males)
Pseudostratified columnar
• Surface cells are columnar
• Secretion, absorption, lubrication, protection,
• Lines most of trachea, primary bronchi,
epididymis and ductus deferens, nasal cavity,
male urethra, large excretory ducts.
• Usually ciliated.
• May contain goblet cells, which secrete
Pseudostratified columnar
Lines nasal cavity & sinuses, auditory tubes, trachea, bronchi
Transitional epithelium
• Surface cells are dome-shaped when
relaxes but flattened when streched.
• Protection, distensible
• Lines urinary tract
Transitional epithelium
Distended bladder
Image from:
Bladder lining, ureters, and superior urethra
Glandular Epithelia - Endocrine & exocrine
• Endocrine Glands Release hormones
into interstitial fluid;
no ducts
• Exocrine Glands Produce secretions
onto epithelial
surfaces; through
Figure 4–6
Modes of Secretion
• Merocrine secretion
– Are produced in Golgi apparatus
– Are released by vesicles
– e.g., sweat glands
• Apocrine secretion
*Are produced in Golgi apparatus
*Are released by shedding cytoplasm
*e.g., mammary glands
• Holocrine secretion
• Are released by cells bursting, killing
gland cells
• Gland cells replaced by stem cells
• e.g., sebaceous gland
Figure 4–6a
Connective Tissue
• Characterized by the cells widely separated from
each other in a matrix that is produced by the
• Tissue protects and supports.
• Cell Matrix composed of two regions
– Ground
• Liquid (sol), Gel, Gum or solid
– Fibers
• Non-elastic (= white or Collagen)
• Elastic (= yellow fibers)
• Types of Connective tissue
Types of Connective Tissue
Loose (Areolar) Connective Tissue
Dense Connective Tissue
Classification of Connective Tissues (3)
• Connective tissue proper:connect and protect
• Fluid connective tissues:transport
• Supportive connective tissues:structural strength
Connective Tissue Proper
• Loose connective
tissue:more ground
substance, less fibers e.g.,
fat (adipose tissue)
• Dense connective
tissue:more fibers, less
ground substance e.g.,
8 Cell Types of Connective Tissue Proper
• Fibroblasts most abundant cell type-in all connective tissue
proper & secrete proteins & hyaluronan (cellular cement)
• Macrophages-large, amoeba-like cells of the immune system:
– eat pathogens and damaged cells, fixed macrophages stay
in tissue, free macrophages migrate
• Adipocytes-fat cells-each cell stores a single, large fat droplet
• Mesenchymal Cells -stem cells that respond to injury or
infection: differentiate into fibroblasts, macrophages, etc.
• Melanocytes -synthesize and store the brown pigment melanin
• Mast Cells -stimulate inflammation after injury or
infection:release histamine and heparin
– Basophils are mast cells carried by blood
• Lymphocytes-specialized immune cells in lymphatic system:
e.g., plasma cells which produce antibodies
• Microphages -phagocytic blood cells: respond to signals from
macrophages and mast cells, e.g., neutrophils and eosinophils
Fibers in Connective Tissue Proper
• Collagen fibers:
– most common fibers in CTP, strong and flexible
– resists force in 1 direction, e.g., tendons and
• Reticular fibers:
– network of interwoven fibers (stroma), strong and
– resists force in many directions, e.g., sheaths
around organs
• Elastic fibers:
– contain elastin, return to original length after
– e.g., elastic ligaments of vertebrae
Ground Substance in Connective
Tissue Proper
• In connective tissue proper and ground
– is clear, colorless, and viscous
– fills spaces between cells and slows
Loose Connective Tissues
• The packing materials of the body
• 3 types in adults: areolar, adipose, reticular
– Areolar Tissue - Least specialized, Elastic fibers, Holds blood vessels
and capillary beds (e.g., under skin (subcutaneous layer))
– Adipose Tissue• White fat:most common, stores fat, slows heat loss (insulation)
• Brown fat: more vascularized, breaks down fat, produces heat
-- Reticular TissueSupportive fibers (stroma) that support functional cells,
reticular organs: spleen, liver, lymph nodes, and bone
Loose Connective Tissue
• Gel like ground with both elastic and non-elastic
fibers running though the ground in many
– Wraps and cushions organs
– Under the skin
Adipose (Fat)
• Function as storage cells for adipose (lipids)
• Adipose cells contain a large vacuole which in
the live cell contains lipids.
• Cell nucleus and cytoplasm are pushed out
to edge of cell membrane.
Dense Connective Tissues
• Connective tissues proper, tightly packed with
high numbers of collagen or elastic fibers:
– dense regular connective tissue
• Attachment and stabilization
• tendons, ligaments
– dense irregular connective tissue
• Interwoven networks of collagen fibers
• layered in skin, around cartilage, around bones, form
capsules around some organs (e.g., liver, kidneys)
– elastic tissue
• made of elastic fibers
• elastic ligaments of spinal vertebrae
Dense Regular Connective
• Nuclei and fibers arranged in parallel rows.
– Tendons and ligaments
– Fibers mostly non-elastic
Fluid Connective Tissues
• Fluid connective tissues:
– blood and lymph
– watery matrix of dissolved proteins
– carry specific cell types (formed elements)
Vascular Tissue (Blood)
• Liquid matrix = plasma
– 90% water
– 10%Plasma proteins, electrolytes, hormones, oxygen,
glucose etc.
• Formed elements
– Erythrocytes -48billion(female) to 54 billion (male) cell
/ ml of blood in humans. Mammals are enucleated
while rest of the vertebrates they have nuclei
– Leukocytes -about 7.5 million / ml of blood
– Platelets -blood clotting
Supportive Connective Tissues
• Support soft tissues and body weight:
– cartilage:
» gel-type ground substance
» for shock absorption and protection
– bone:
» calcified (made rigid by calcium salts, minerals)
» for weight support
• Cartilage Matrix – Proteoglycans, ground
substance proteins, cells (chondrocytes)
surrounded by lacunae (chambers)
• Cartilage Structure
– No blood vessels:chondrocytes produce
antiangiogenesis factor
– Perichondrium:outer, fibrous layer (for strength),
inner, cellular layer (for growth and maintenance)
• Ground of matrix is gum like.
• Cells are found in Lacunae within the matrix.
• Fibers may be elastic or non-elastic, or a form
of non-elastic called reticular(where the nonelastic fibers of very thin)
– Hyaline Cartilage-example on the ends of bones
– Elastic Cartilage- example ear cartilage
– Non-elastic Cartilage- example nose cartilage.
Types of Cartilage (3)
Hyaline cartilage, Elastic cartilage, Fibrocartilage
• Hyaline cartilage:
– stiff, flexible support
– reduces friction between bones
– found in synovial joints, rib tips, sternum, and
Hyaline cartilage
• Elastic cartilage:
– supportive but
bends easily
– found in external
ear and epiglottis
• Fibrocartilage
– Limits movement
– Prevents bone-to-bone
– Pads knee joints
– Found between pubic
bones and intervertebral
Elastic Cartilage
– Ground of matrix is Solid (Calcium
– Has blood supply and nerves running
through the Haversian canal systems.
• Also called osseous tissue:
– strong (calcified: calcium salt deposits)
– resists shattering (flexible collagen fibers)
• Bone Cells - Osteocytes:
– arranged around central canals within matrix
– small channels through matrix (canaliculi) access blood supply
• Periosteum:
– covers bone
– fibrous layer
– cellular layer
How do epithelial and connective tissues combine to
form 4 types of membranes?
• Membranes - are physical barriers that line or
cover portions of the body consisting of an
epithelium and supported by connective tissues
4 Types of Membranes
1. Mucous
2. Serous
3. Cutaneous
4. Synovial
• Mucous membranes (mucosae):
– line passageways that have external connections
– also in digestive, respiratory, urinary, and
reproductive tracts
• Mucous Tissues
– Epithelial surfaces must be moist to reduce friction,
to facilitate absorption and excretion
– Lamina propria is areolar tissue
Serous Membranes
Line cavities not open to the outside
Are thin but strong
Have fluid transudate to reduce friction
double, have a
parietal portion
covering the cavity • Pleural membrane lines pleural
cavities covers lungs
and a visceral
• Peritoneum lines peritoneal cavity
portion (serosa)
covers abdominal organs
covering the
• Pericardium lines pericardial
cavity covers heart
• Cutaneous membrane:
– is skin, surface of the body
– thick, waterproof, and dry
How do connective tissues form the
framework of the body?
• Connective tissues:
– provide strength and stability
– maintain positions of internal organs
– provides routes for blood vessels, lymphatic
vessels, and nerves
• fascia:
– the body’s framework of connective tissue
– layers and wrappings that support or surround
3 Types of Fasciae
• Superficial fascia
• Subserous fascia
• Deep fascia
Figure 4–17
What are the structures and functions of
the three types of muscle tissue?
3 Types of Muscle Tissue
• Skeletal muscle:
– large body muscles responsible for movement
• Cardiac muscle:
– found only in the heart
• Smooth muscle:
– found in walls of hollow, contracting organs (blood
vessels; urinary bladder; respiratory, digestive and
reproductive tracts)
Classification of Muscle Cells
• Striated (muscle cells with a banded
– or nonstriated (not banded)
• Muscle cells can have a single nucleus:
– or be multinucleate
• Muscle cells can be controlled voluntarily
– or involuntarily (automatically)
Muscle Tissue
• Tissue with cells having fibers specialized for
– Skeletal Muscle (Striated, voluntary)
• Parallel elongated cells (fibers)
• multinucleated and each cell is the length of the
• Light meat, Dark meat—Slow twitch, fast twitch muscle
– Smooth Muscle (Visceral, involuntary)
• Cells are long and tapered.
• Organized into sheets of muscle.
– Cardiac Muscle
• Intercalated disc
• Myogenic
• branched
• Skeletal muscle cells:
– Striated, voluntary, and ultinucleated
– are long and thin
– are usually called muscle fibers
– do not divide
– new fibers are produced by stem cells (satellite
Figure 4–18a
Skeletal Muscle
• Cardiac muscle cells:
– are called cardiocytes
– form branching networks connected at intercalated
– are regulated by pacemaker cells
– striated, involuntary, and single nucleus
Cardiac Muscle
• Smooth muscle cells:
– are small and tapered
– can divide and regenerate
– nonstriated, involuntary, and single nucleus
Smooth Muscle
What is the basic structure and role
of neural tissue?
• Neural tissue is concentrated in the central
nervous system:
– brain
– spinal cord
2 Kinds of Neural Cells
1. Neurons:
– nerve cells
– perform electrical communication
2. Neuroglia:
– support cells
– repair and supply nutrients to neurons
Nervous Tissue
• Cells specialized to polarize and
• Cell is a neuron
• Cell body:
Cell Parts of a Neuron
– contains the nucleus and nucleolus
• Dendrites:
– short branches extending from the cell body
– receive incoming signals
• Axon (nerve fiber):
– long, thin extension of the cell body
– carries outgoing electrical signals to their destination
Figure 4–19
End of Tissue presentation