Transcript Anatomy & Physiology

Anatomy & Physiology
Lesson 4
HISTOLOGY
 Histology
is the study of the structure of
tissues.
 A tissue is a group of similar cells and
their intercellular substance, function
together to perform a specialized activity.
 Tissues in the body can be classified into
four principle types, according to their
structure and function.
TYPES OF TISSUES

Epithelial tissue—covers body surfaces, lines
hollow organs, body cavities, and ducts, and
forms glands.
 Connective tissue—protects and supports the
body and its organs, binds organs together,
stores energy reserves as fat, and provides
immunity.
 Muscle tissue—responsible for movement and
generation of force.
 Nervous tissue—initiates and transmits action
potentials (nerve impulses) that help coordinate
body activities.
EPITHELIAL TISSUE
 Epithelial
tissue (or epithelium) can be
divided into two types:
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Covering and lining epithelium—forms skin,
outer covering of some organs, lines body
cavities and the inside of the respiratory and
digestive tracts, blood vessels, and ducts.
Glandular epithelium—forms the secreting
portion of glands.
GENERAL FEATURES OF
EPITHELIAL TISSUES

Consist of mostly or entirely tightly packed cells with little
or no extracellular material between cells.
 Cells are arranged in continuous sheets, in either single
or multiple layers.
 Cell layers have an apical (free) surface, which is
exposed to a body cavity, lining of an internal organ, or
the exterior of the body, and a basal surface, which is
attaced to the basement membrane.
 Cells have many junctions, providing secure attachments
between cells.
 Tissues are avascular—blood vessels that supply
nutrients and remove wastes are located in the adjacent
connective tissue. Materials move between epithelium
and connective tissue by diffusion.
 Have a nerve supply.
 Diverse in origin—are derived from all three primary
germ layers.
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GENERAL FEATURES OF
EPITHELIAL TISSUES
Adhere firmly to adjacent connective tissue, which holds
the epithelium in place and prevents it from tearing.
Connection between the epithelium and the connective
tissue is via a thin basement membrane, which is
composed of the basal lamina (collagen, laminin, and
proteoglycans) and the reticular lamina (reticular fibers,
fibroconectin, and glycoproteins). The basement
membrane provides cell attachment and physical
support for the epithelium, acts a filter in the kidneys,
and guides cell migration during development and tissue
repair.
 Have a high capacity for renewal (high mitotic rate)
because they are subject to wear and tear and injury.
 Functions include: protection, filtration, lubrication,
secretion, digestion, absorption, transportation,
excretion, sensory reception, and reproduction.
EPITHELIAL TISSUE
TYPES OF EPITHELIAL TISSUE
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Simple squamous epithelium
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Description: Single layer of flat cells.
Location: Lines heart, blood vessels, lymphatic
vessels, air sacs of lungs, glomerular capsule of
kidneys, and inner surface of the eardrum. Forms
epithelial layer of serous membranes.
Function: Filtration, diffusion, osmosis, and secretion
in serous membranes.
TYPES OF EPITHELIAL TISSUE
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Simple cuboidal epithelium:
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Description: Single layer of cube-shaped cells.
Location: Covers surface of ovary, lines anterior
surface of eye lens capsule, forms pigmented
epithelium at back of eye, lines kidney tubules and
smaller ducts of many glands.
Function: Secretion and absorption.
TYPES OF EPITHELIAL TISSUE
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Nonciliated simple columnar epithelium:
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Description: Single layer of nonciliated rectangular
cells. Contains goblet cells (secrete mucus) and
microvilli (fingerlike projections that increase the
plasma membrane surface area) in some locations.
Location: Lines GI tract from the stomach to the anus,
ducts of many glands, and gallbladder.
Function: Secretion and absorption.
TYPES OF EPITHELIAL TISSUE
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Ciliated simple columnar
epithelium:
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Description: Single layer of ciliated
rectangular cells. Contains goblet
cells in some locations.
Location: Lines a few portions of
upper respiratory tract, Fallopian
tubes, uterus, some paranasal
sinuses, and central canal of
spinal cord.
Function: Moves fluids or particles
along a passageway by ciliary
action.
TYPES OF EPITHELIAL TISSUE
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Stratified squamous
epithelium:
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Description: Multiple cell layers.
Deep layers are cuboidal to
columnar in shape. Superficial
layers consist of squamous cells.
As surface cells are lost, they are
replaced by basal cells.
Location: Keratinizing variety
forms superficial layer of skin.
Nonkeratinizing variety lines wet
surfaces, such as lining of the
mouth, esophagus, part of
epiglottis, vagina, and covers
tongue.
Function: Protection.
TYPES OF EPITHELIAL TISSUE
 Stratified
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cuboidal epithelium:
Description: Two or more layers of cells in
which the superficial cells are cube-shaped.
Location: Ducts of adult sweat glands and
part of male urethra.
Function: Protection.
TYPES OF EPITHELIAL TISSUE
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Stratified columnar
epithelium:
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Description: Several layers of
polyhedral cells. Columnar
cells are only in the superficial
layer.
Location: Lines part of urethra,
large excretory ducts of some
glands, small areas in anal
mucus membrane, and part of
the conjuctiva of the eye.
Function: Protection and
secretion.
TYPES OF EPITHELIAL TISSUE
 Transitional
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epithelium
Description: Appearance is
variable. Shape of
superficial cells ranges from
squamous to cuboidal,
depending on the degree of
distention (stretching).
Location: Lines urinary
bladder and portions of
ureters and urethra.
Function: Permits
distention.
TYPES OF EPITHELIAL TISSUE
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Pseudostratified columnar epithelium:
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Description: Not a true stratified tissue. Nuclei of cells
are at different levels. All cells are attached to the
basement membrane, but not all reach the free
surface.
Location: Ciliated lines most of upper respiratory tract.
Nonciliated lines larger ducts of many glands,
epididymis, and part of male urethra.
Funtion: Secretion and movement of mucus by ciliary
action.
TYPES OF EPITHELIAL TISSUE
(GLANDULAR)
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Exocrine glands:
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Description: Secretory products released into ducts.
Location: Sweat, oil, ear wax, and mammary glands
of the skin, digestive glands (like salivary glands and
pancreas).
Function: Produce mucus, perspiration, oil, ear wax,
milk, or digestive enzymes.
Endocrine glands:
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Description: Secretory products (hormones) diffuse
into blood after passing through extracellular fluid.
Location: Pituitary gland, pineal gland, thyroid and
parathyroid glands, adrenal glands, pancreas,
ovaries, testes, thymus gland, etc.
Function: Produce hormones that regulate various
body activities.
CONNECTIVE TISSUE
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Connective tissue is the most abundant, widely
distributed (and diverse) tissue in the body. It can be
divided into two classifications, with several subclasses:
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Embryonic connective tissue
• Mesenchyme
• Mucous connective tissue
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Mature connective tissue
• Loose connective tissue
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Areolar connective tissue
Adipose connective tissue
Reticular connective tissue
• Dense connective tissue
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Dense regular connective tissue
Dense irregular connective tissue
Elastic connective tissue
• Cartilage
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Hyaline cartilage
Fibrocartilage
Elastic cartilage
• Bone (osseous) tissue
• Blood (vascular tissue)
GENERAL FEATURES OF
CONNECTIVE TISSUE
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Consists of three basic elements: Cells, ground
substance, and fibers. Together, the ground substance
and fibers form the extracellular matrix. Connective
tissue cells are surrounded by large amounts of matrix,
so they seldom touch eachother.
Connective tissues usually do not occur on free
surfaces. However, joint cavities are lined by areolar
connective tissue.
Except for cartilage, connective tissue has a nerve
supply.
Usually is highly vascular (has a rich blood supply).
Exceptions are cartilage (no blood supply) and tendons
(scant blood supply).
The matrix, which may be fluid, semifluid, gelatinous,
fibrous, or calcified, is usually secreted by the connective
tissue cells and adjacent cells and determines the
tissue’s physical qualities.
CONNECTIVE TISSUE CELLS
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Derived from embryonic mesodermal cells
(mesenchymal cells).
 The immature cells have names that end in –
blast (fibroblasts, chondroblasts, osteoblasts).
These cells retain the ability to undergo mitosis
and produce matrix.
 The mature cells have names that end in –cyte
(chondrocyte, osteocyte). Mature cells have
decreased capacity for cell division and matrix
formation. They are mostly responsible for
maintaining the matrix.
CONNECTIVE TISSUE CELLS
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Some connective tissue cells include:
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Fibroblasts—Large, flat, spindle-shaped cells with branching
processes. Secrete the molecules that form the matrix.
Macrophages (histiocytes)—Develop from monocytes (a type
of white blood cell). Irregular shape with short, branching
projections that engulf bacteria and cellular debris by
phagocytosis, providing defense for the body. Wandering
macrophages leave the blood and travel to infected tissues while
fixed macrophages remain in certain tissues and organs.
Plasma cells—Small and either round or irregularly shaped.
Develop from B lymphocytes (a type of white blood cell).
Secrete antibodies and provide immunity. Found throughout the
body, but mostly in connective tissues—especially in the GI tract
and mammary glands.
Mast cells—Abundant alongside blood vessels. Produce
histamine, which dilates small blood vessels during
inflammation.
CONNECTIVE TISSUE MATRIX
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Ground Substance:
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Supports cells, binds them together, provides a medium for
transport of substances between blood and cells, influences
tissue development, migration, proliferation, shape, and
metabolic functions of tissues.
Contains a variety of large, complex molecules, including:
• Hyaluronic acid—viscous, slippery substance that binds cells
together, lubricates joints, and help maintain shape of eyeball.
• Chondroitin sulfate—jellylike substance that provides support and
adhesiveness in cartilage, bone, skin, and blood vessels.
• Dermatan sulfate—exists in skin, tendons, blood vessels, and
heart valves.
• Keratan sulfate—exists in bone, cartilage, and the cornea of the
eye.
• Adhesion proteins—(fibronectin, laminin, collagen, fibrinogen)
interact with receptors on plasma membranes to anchor cells in
position and provide traction for cell movement.
CONNECTIVE TISSUE MATRIX
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Fibers
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Synthesized by fibroblasts. Provide strength and support for
tissues.
• Collagen fibers—at least five different types. Very tough and
resistant to pulling forces, yet allow some flexibility in the tissue.
Often occur in bundles composed of many tiny fibrils lying parallel to
each other. Bundle arrangement provides great strength.
Composed of the protein collagen (most abundant protein in the
body). Found in most CT types—especially bone, cartilage,
tendons, and ligaments.
• Elastic fibers—smaller diameter than collagen fibers. Branch and
join together to form a network within a tissue. Composed of the
protein elastin and the large glycoproteins (especially fibrillin).
Provide strength. Can be stretched up to 150% of their relaxed
length without breaking. Plentiful in skin, blood vessel walls, and
lung tissue.
• Reticular fibers—consist of collagen and a glycoprotein coating.
Much thinner that collagen fibers and form a branching network.
Provide support in blood vessel walls. Form a network around fat
cells, nerve fibers, and skeletal and smooth muscle cells. Provide
support and strength and form the stroma (supporting framework)
of many soft organs (spleen, lymph nodes). Help form basement
membrane.
TYPES OF CONNECTIVE TISSUE
(EMBRYONIC)
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Mesenchyme
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Description: Irregularly shaped mesenchymal cells
embedded in a semifluid ground substance that
contain delicate reticular fibers.
Location: Deep to skin, along developing embryonic
bones. Some mesenchymal cells found in adult CT—
especially along blood vessels.
Function: Forms all other kinds of CT.
Mucous connective tissue
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Description: Star-shaped cells embedded in a
viscous, jellylike ground substance that contain fine
collagen fibers.
Location: Umbilical cord.
Function: Support.
TYPES OF CONNECTIVE TISSUE
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Areolar connective tissue
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Description: Fibers (collagen, elastic, and reticular) and
several kinds of cells (fibroblasts, macrophages, plasma
cells, adipocytes, and mast cells) embedded in a semifluid
ground substance.
Location: Subcutaneous layer of skin, papillary (superficial)
region of dermis of skin, mucous membranes, blood vessels,
nerves, and around body organs.
Function: Strength, elasticity, support.
TYPES OF CONNECTIVE TISSUE
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Adipose tissue
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Description: Consists of adipocytes, specialized cells that store
triglycerides (fats and oils) in a large central area. Nuclei are peripherally
located.
Location: Subcutaneous skin layer, around heart and kidneys, yellow
bone marrow of long bones, padding around joints, and behind eyeball in
eye socket.
Function: Heat regulation, energy reserve, support and protection. In
newborns, brown fat generates heat to help maintain body temperature.
TYPES OF CONNECTIVE TISSUE
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Reticular connective tissue
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Description: Network of interlacing reticular fibers and
reticular cells.
Location: Stroma (framework) of liver, spleen, lymph nodes.
Red bone marrow that gives rise to blood cells. Reticular
lamina of basement membrane.
Function: Forms stroma of organs. Binds smooth muscle
tissue cells together.
TYPES OF CONNECTIVE TISSUE
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Dense regular connective tissue:
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Description: Matrix has shiny white appearance. Mostly
composed of collagen fibers arranged in parallel bundles.
Fibroblasts present in rows between bundles.
Location: Tendons, most ligaments, and aponeuroses
(sheetlike tendons that attach muscle to other muscle or
bones).
Function: Provides strong attachment between various
structures.
TYPES OF CONNECTIVE TISSUE
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Dense irregular connective tissue
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Description: Predominantly collagen fibers, randomly arranged,
and a few fibroblasts. Usually forms a sheet.
Location: Fascia, reticular (deeper) region of dermis of skin,
perichondrium (membrane around cartilage), periosteum
(membrane around bone), joint capsules, dura mater (outer
membrane around brain and spinal cord), membrane capsules
around various organs, heart valves.
Function: Provides strength.
Elastic connective tissue
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Description: Predominantly freely branching elastic fibers.
Fibroblasts present in spaces between fibers.
Location: Lung tissue, walls of elastic arteries, trachea, bronchial
tubes, true vocal cords, suspensory ligament of penis, and
ligamenta flava of vertebrae (ligaments between vertebrae).
Function: Allows stretching of various organs.
TYPES OF CONNECTIVE TISSUE
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Hyaline cartilage
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Description: Bluish-white, shiny ground substance with fine
collagen fibers. Contains numerous chondrocytes. Most
abundant type of cartilage.
Location: Ends of long bones, anterior ends of ribs, nose,
parts of larynx, trachea, bronchi, bronchial tubes, embryonic
skeleton.
Function: Provides smooth surfaces for movement at joints,
flexibility, and support.
TYPES OF CONNECTIVE TISSUE
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Fibrocartilage
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Description: Chondrocytes scattered among bundles
of collagen fibers within the matrix.
Location: Pubic symphysis, intervertebral discs,
menisci (cartilage pads) of knees.
Function: Support and fusion.
Elastic cartilage
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Description: Chondrocytes located in a threadlike
network of elastic fibers within the matrix.
Location: Epiglottis of larynx, external ear, auditory
(Eustacian) tubes.
Function: Support and shape maintenance.
TYPES OF CONNECTIVE TISSUE
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Bone (osseous) tissue
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Description: Compact bone consists of osteons
(Haversian systems) that contain lamellae, lacunae,
osteocytes, canaliculi, and central (Haversian) canals.
Spongy bone consists of thin plates called
trabeculae with red bone marrow between the
trabeculae.
Location: Both compact and spongy bone form the
various parts of the body’s bones.
Function: Support, protection, storage, houses bloodforming tissue, serves as levers that act with muscles
to provide body movement.
TYPES OF CONNECTIVE TISSUE
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Bone (osseous) tissue
TYPES OF CONNECTIVE TISSUE
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Blood (vascular tissue)
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Description: Plasma and formed elements. Formed
elements are erythrocytes (red blood cells),
leukocytes (white blood cells), and platelets.
Location: Within blood vessels (arteries, arterioles,
capillaries, venules, and veins).
Function: Erythrocytes transport oxygen and carbon
dioxide. Leukocytes are involved in phagocytosis,
allergic reactions, and immunity. Platelets are
essential for blood clotting.
TYPES OF CONNECTIVE TISSUE
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Blood (vascular tissue)
MEMBRANES
 Epithelial
membrane—The combination
of an epithelial layer and the underlying
connective tissue layer. Principal epithelial
membranes are:
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Mucous membrane
Serous membrane
Cutaneous membrane—Skin. An organ of
the integumentary system. Will be discussed
later.
 Synovial
membrane—Contains
connective tissue only—no epithelium.
MUCOUS MEMBRANES
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Line body cavities that open directly to the exterior
(entire digestive, respiratory, and reproductive systems,
and much of the urinary system).
Consist of a lining layer of epithelium and an underlying
layer of connective tissue
Epithelial layer provides barrier against microbes and
other pathogens, secretes mucus (moisturizes body
cavities, traps particles in the respiratory tract, and
lubricates food), secretes enzymes digestive enzymes,
and is the site for food and fluid absorption in the GI
tract.
Connective tissue layer is called the lamina propria. It
binds the epithelium to underlying structures while
allowing some flexibility, holds blood vessels in place,
and protects underlying muscles from abrasion or
puncture. Oxygen and nutrients diffuse from the lamina
propria to the epithelial layer while carbon dioxide and
wastes diffuse in the opposite direction.
SEROUS MEMBRANES
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Line body cavities that do not open to the exterior and
cover the organs lying within those cavities.
Composed of two layers:
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Parietal layer—attached to the cavity wall.
Visceral layer—attached to and covering the organs within the
cavity.
Epithelial layer secretes a watery fluid called serous
fluid, which allows organs to glide freely against each
other and against the cavity wall.
Epithelial layer is composed of mesothelium (simple
squamous epithelium).
Connective tissue layer is composed of a thin layer of
areolar CT.
Serous membrane of the thoracic cavity is called the
pleura, of the pericardial cavity is the pericardium, and
of the abdominal cavity is the peritoneum.
SYNOVIAL MEMBRANES
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Do not contain epithelium.
Line cavities that do not open to the exterior.
Line the cavities of freely movable joints, bursae
(cushioning sacs), and tendon sheaths in our
hands and feet.
Composed of areolar CT, with elastic fibers and
varying amounts of fat.
Secrete synovial fluid, which lubricates the
cartilage at the end of bones during movement
and nourishes the cartilage at joints.
MUSCLE TISSUE
 Muscle
tissue consists of fibers (cells) that
are designed to generate force for
contraction. It provides motion, maintains
posture, and generates heat. Muscle
tissue is classified into three types, based
on location, structure, and function:
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Skeletal muscle tissue
Cardiac muscle tissue
Smooth muscle tissue
TYPES OF MUSCLE TISSUE
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Skeletal muscle tissue
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Description: Long, cylindrical, striated (having alternating
light and dark bands) fibers with many peripherally located
nuclei. Voluntary control (can be made to contract or relax
by conscious control).
Location: Usually attached to bones by tendons.
Function: Motion, posture, heat production (thermogenesis).
TYPES OF MUSCLE TISSUE
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Cardiac muscle tissue
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Description: Branched, striated fibers with one or two
centrally located nuclei. Contains intercalated discs
(unique end-to-end attachments between muscle fibers).
Involuntary control (contractions are usually not under
conscious control).
Location: Heart wall.
Function: Pumps blood to all parts of the body.
TYPES OF MUSCLE TISSUE
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Smooth muscle tissue
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Description: Spindle-shaped, nonstriated (smooth) fibers with one
centrally located nucleus. Usually involuntary control.
Location: Walls of hollow internal structures such as blood vessels,
airways to the lungs, stomach, intestines, gallbladder, urinary bladder,
and ureters.
Function: Motion (constriction of blood vessels/airways, propulsion of
food through GI tract, contraction of urinary bladder/gallbladder).
NERVOUS TISSUE
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Composed of only two principal cell types:
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Neurons—Nerve cells. Convert stimuli into nerve
impulses, which they conduct to other neurons,
muscle tissue, or glands. Most neurons consist of:
• Cell body—contains the nucleus and other typical
organelles.
• Dendrites—tapering, highly branched, usually short
extensions that are the major input receiving portions of
neurons.
• Axon—single, thin, cylindrical process that may be very long.
Output portion of a neuron—conducts nerve impulses toward
another neuron or other tissue.
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Neuroglia—Do not generate or conduct nerve
impulses but do perform many important support
functions in nervous tissue.
NERVOUS TISSUE
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Description: Consists of
neurons and neuroglia.
Location: Nervous system.
Function: Exhibits sensitivity
to various stimuli, converts
stimuli into nerve impulses,
and conducts nerve impulses
to other neurons, muscle
fibers, or glands.