Tissues and Membranes

Anatomy chapter 5

Body Tissues

• A tissue is a group of cells that have similar structures and that function together as a unit.

• Histology – the microscopic study of tissues.

• There are 4 main tissue types in the body:

Epithelial Muscle

Connective Nervous

Tissue types

EPITHELIAL TISSUE

Epithelial Tissue• Widespread throughout the body

• Cover body surfaces• Line body cavities• Major tissue in glands• It always has a free surface – exposed to the

outside or to open space internally• Jobs include protection, secretion, absorption,

filtration, diffusion, and sensory reception

Epithelial Tissue types

Epithelial tissue

• Tightly packed cells – very little intercellular matrix (the substance between cells)

• Cells are attached to underlying tissue by the basement membrane, which is nonliving. • The basement membrane is a mixture of

carbohydrates and proteins.

Basement membrane

The epithelial cells above receive their nutrients by diffusion from the blood vessels in the underlying tissues.

Epithelial tissue

• Are avascular – which means they have no blood supply directly.

• Reproduce quickly (divide readily)

• Are classified according to cell shape and number of layers in the tissue.

Epithelial types

Squamous cells are flat; the nuclei are broad and thin.

Cuboidal – cubelike, the nuclei are spherical and centrally located.

Columnar – are tall and narrow, nuclei are usually near the base

Simple squamous epithelium

• A single layer of thin, flat cells that fit closely together.

• Alveoli in lungs• Capillary walls• Tissue is damaged

easily.

Simple squamous

Simple Cuboidal Epithelium

• A single layer of cube shaped cells.

• Linings of many glands• Lining of kidney

tubules• Absorption and

secretion

Simple Cuboidal

Simple Columnar Epithelium• Single layer of cells

that are taller than they are wide.

• Lining the stomach and intestines, also lines the uterus

• Secretes digestive enzymes, absorbs nutrients

Simple columnar

Simple columnar

• Where absorption is necessary, these cells may have microvilli.

• Goblet cells secrete mucus.

• Cilia may be present

Pseudostratified Columnar Epithelium

• Appears to have multiple layers, but it really does not.

• All cells attached to basement membrane.

• Commonly have cilia• Usually in respiratory

and male reproductive tract.

Pseudostratifed Columnar

Stratified Squamous Epithelium

• The most common type of layered epithelium.

• Many layers of cells.• Cuboidal at the

basement membrane, become thinner near the surface.

Stratified Squamous

Stratified Squamous• Cells at the basement membrane undergo

mitosis.

• The cells die as they are pushed further from the basement membrane.

• Outer layer of skin

• As skin cells age, they accumulate keratin (a protein) and then harden and die.

Stratified Cuboidal Epithelium

• Two or three layers of cuboidal cells that form a lining of the lumen.

• More protection than 1 layer.

• Lines sweat, salivary and mammary glands, also the pancreas

Stratified Columnar Epithelium

• Several layers of cells.• Superficial layer are

columnar, basal layers are cuboidal.

• Found in the pharynx, also in the male urethra.

Transitional Epithelium

• A specialized type of tissue with several layers, but can be stretched in response to tension.

• The lining of the bladder is an example.

Transitional epithelium

Glandular epithelium

• Consists of cells that are specialized to produce and secrete substances.

• Lies deep (underneath) epithelium that cover and line parts of the body.

• Exocrine glands secrete their products onto a free surface via a duct.

Types of glandular epithelium

• Simple tubular – the ducts have no branches.

• The gland and duct merge with no change in diameter.

Types of glandular epithelium

• Compound acinar• Has branches

(compound)• Has sacs (acinar)• This type is also called

alveolar

Gland classified by mode of secretion

• Merocrine glands – use exocytosis, no cytoplasm is lost. Example: salivary glands

• Apocrine glands – Product accumulates in an area of the gland, then is pinched off – a small portion of the cell is lost. Example: sweat glands

• Holocrine – the entire cell ruptures, releasing products. Example: Oil (sebaceous) glands

CONNECTIVE TISSUE

Connective tissue

• Binds structures together

• Form a framework and support for organs and the body.

• Store fat

• Transport substances

• Protect against disease and repair tissue damage.

Connective tissue• Cells can reproduce, but not as quickly as

epithelial tissue.

• Three types of fibers embedded in intercellular matrix – collagenous fibers, elastic fibers and reticular fibers.

• Many cell types in connective tissue. Most common are mast cells, macrophages, and fibroblasts

Connective tissue cells

• Fibroblasts – Most common. Large cells secrete proteins into the extracellular matrix.

• Macrophages – Originate as white blood cells and carry on phagocytosis. Can move about

• Mast Cells – Large cells usually near blood vessels. They release heparin and histamine.

Fibers• Collagenous fibers – thick threads of the protein

collagen. Grouped in bundles. Flexible but only slightly elastic. Important parts of ligaments and tendons.

• Elastic – composed of the protein elastin. Weaker than collagenous, but stretch easily. Vocal cords.

• Reticular – Very thin collagenous fibers. Highly branched and form a supporting network in organs like the spleen

Types of connective tissue• Loose connective tissue

• Adipose tissue

• Elastic connective tissue

• Dense fibrous connective tissue

• Cartilage

• Bone

• Blood

Loose connective tissue

Loose connective tissue

• Also called areolar CT• Packing material in the

body• Attaches skin to

underlying tissue, fills spaces between muscles.

Adipose tissue

• Better known as fat• Cells can take up fat

and release it at a later date.

• Acts as a cushion for the body, insulator for heat.

Reticular connective tissue

Dense Fibrous Connective Tissue

• Closely packed parallel bundles of collagenous fibers.

• Make up tendons and ligaments

Elastic Connective Tissue

• Closely packed elastic fibers.

• Yields easily to pulling force.

• Vocal cords and vertebral ligaments

Cartilage

• Has an abundant matrix – solid, yet flexible

• Cartilage cells are called chondrocytes

• Heals slowly – no direct blood supply

• Protects underlying tissues, supports structures, and is a framework

3 types: hyaline, fibrocartilage, and elastic

Hyaline cartilage

Hyaline: most common type

Found at the end of long bones

Most of the fetal skeleton is made of this before it is replaced by bone

Fibrocartilage

• Abundance of strong collagenous fibers.

• Acts as shock absorber• Found in between

vertebrae and between the bones in the knee joint.

Elastic Cartilage

• Much more flexible than hyaline or fibrocartilage.

• Found in outer ear.

Bone

• Most rigid connective tissue

• Arranged in concentric rings

• Form a framework for body, and attach muscles

Bone tissue

Blood

• Unique because it has a liquid matrix.

• Erythrocytes – red blood cells

• Leukocytes – white blood cells

• Plasma – liquid matrix

• Platelets – fragment of a cell in the bone marrow.

Blood

Blood components

• Red blood cells

• White blood cells

• Platelets

• Plasma – plasma is 95% water• Other 5% is salts, nutrients, hormones, and

proteins.

Web sites

• Goto http://msjensen.cehd.umn.edu/default.asp

• Click on image bank and review some images of types of tissue

• Click on self-test and choose a test to take. Use your notes and identify tissue types and structures.

MUSCLE TISSUE

Muscle Tissue

• Made up of cells that have an ability to shorten or contract to produce movement.

• Highly cellular – good blood supply

• Arranged usually in bundles or layers.

• 3 types: skeletal, cardiac, and smooth

Types of muscle tissue

Skeletal muscle

• What we usually think of as “muscle”

• 40% of body weight• Fibers are long and

cylindrical with many nuclei

• Cell has a striated appearance.

Skeletal muscle

• Muscle fibers are collected into bundles and wrapped in connective tissue.

• Skeletal muscle is voluntary

Smooth muscle

• Found in the walls of hollow body organs – stomach, intestines, etc.

• Lacks striations• Also called involuntary

muscle

Cardiac muscle

• Found only in the heart wall.

• Look similar to striated muscle

• One nucleus per cell• Involuntary contraction

NERVOUS TISSUE

Nervous tissue

• Found in brain, spinal cord and nerves

• Responsible for coordinating and controlling body activities.

• Communicates by way of electrical nerve impulses.

• Nerve cells - neurons

Neurons

INFLAMMATION AND TISSUE REPAIR

Inflammation

• A defense mechanism that attempts to contain tissue injury and prepare for healing.

• Symptoms: redness, swelling, heat, pain.

• It is a beneficial process, even though it may be painful.

Inflammatory process

• Blood vessels dilate, become more permeable

• Increased blood flow to area

• Fluid and WBC’s leave vessels and go into tissue space. WBCs engulf debris and bacteria.

• Fluid dilutes toxins and contains clotting proteins.

Tissue Repair

Regeneration

• Replacement of destroyed tissue by proliferation of identical cells.

• Occurs only in tissues that can undergo mitosis

• Skeletal muscle, cardiac muscle, and nerve tissue cannot regenerate.

Fibrosis

• Replacement of destroyed tissue by fibrous (scar) tissue

• Collagen fibers form the basis of the scar.

• Immature scar tissue is called granulation tissue.

• Scar may be visible or not depending on the severity of the wound.

BODY MEMBRANES

Body Membranes

• Thin sheets of tissue that cover the body, line body cavities, cover organs, and line the cavities in hollow organs.

• Skin is a membrane

• Membranes may be epithelial or connective tissue.

Epithelial membranes

Mucous membranes

• Epithelial tissue that is attached to loose connective tissue.

• Line the body cavities that open to the outside

• Examples: digestive tract, respiratory, excretory, and reproductive tracts.

Serous membranes

• Line body cavities that do not open directly to the outside.

• Thin layer of loose connective tissue covered by a layer of simple squamous epithelium.

• Covered by a thin layer of serous fluid.

Mucous membranes

Serous membranes

Connective tissue membranes

Synovial membranes

• Line the cavities of the freely moveable joints, like the shoulder, elbow and knee.

• They secrete synovial fluid into the joint cavity, which lubricates the cartilage.

Meninges

• Connective tissue coverings around the brain and spinal cord.

• Provide protection.

• Meningitis is inflammation of the meninges.

Synovial membranes

Meninges

Meninges

Cell communication

• Interactions between cells are vital to the function of other cells, tissues, and organs.

• All cells are signaled to survive and carry out homeostasis (maintenance of a constant internal state).

• All cells need energy to carry out functions.

Methods of cell communication

• Most common way that cells communicate is by chemical means.• Hormones • Signal receptors (like a lock and key)• Proteins

Specific examples of hormone communication

• Cell division

• Immune response

• Production of enzymes or proteins

• Blood clotting

Other methods of cell communication

• Cell to cell contact

• Electrical impulses (SA node in the heart, axons in the nervous system)