MEDI 101 Body Tissues

• MEDI 101 is the course title.
• The lectures will be on body tissues.
• Dr. Hisham Alshaikhli, Assistant Professor at the College of Nursing, Qatar University, is teaching the course.
• Office hours are on Mondays and Wednesdays from 12 pm-1 pm in Building 103, Office 504.

Learning Objectives

• The course covers body tissues and membranes.
• Epithelial tissue
• Classification of epithelial tissues
• Glandular tissues
• Classification of glandular tissues
• Classification of connective tissues
• Bone and cartilage
• Muscle tissue
• Nervous tissue
• Classification of tissue membranes

Body Tissues

• Tissues are groups of cells with similar structure and function.
• The four primary tissue types are epithelial, connective, muscle, and nervous tissue.

Epithelial Tissue

• Epithelial tissue is located in body coverings, body linings, and glandular tissue.
• It functions in protection, absorption, filtration, and secretion.

Classification of Epithelia

• Hallmarks of this tissue include covering/lining body surfaces.
• Often forms sheets with a free apical surface and an anchored basal surface via the basement membrane, allowing growth and regeneration.
• It is avascular (no blood supply).
• It regenerates easily if well nourished.
• Epithelia are classified by the number of cell layers and the shape of the cells.
• Cell layer types are simple (one layer) and stratified (more than one layer).
• Cell shape types are squamous (flattened), cuboidal (cube-shaped, like dice), and columnar (shaped like columns).
• Simple epithelia are one layer.
• Stratified have multiple layers.

Simple Squamous Epithelium

• Simple epithelia are flat and simple, existing as one layer.
• It functions in absorption, secretion, and filtration.
• The tissue is very thin, so not well-suited for protection.
• Locations exist in membranes of flat cells, and usually to form membranes.
• Lines air sacs of the lungs and forms walls of capillaries and serous membranes (serosae) that line and cover organs in the ventral cavity.
• Functions in diffusion, filtration, or secretion.

Simple Cuboidal Epithelium

• This tissue exists as a single layer of cube-like cells.
• Is often found in glands and their ducts, and lines the walls of kidney tubules and covers surface of ovaries.
• Functions in secretion and absorption, also ciliated types propel mucus or reproductive cells.

Simple Columnar Epithelium

• This tissue exists as a single layer of tall cells
• Goblet cells secrete mucus
• Locations include the lining of the digestive tract from stomach to anus + Mucous membranes line body cavities opening to the exterior
• These function in secretion and absorption; ciliated types propel mucus or reproductive cells

Pseudostratified Columnar Epithelium

• All cells rest on a basement membrane
• It exists as a single layer, but some cells are shorter than others giving the appearance of having stratification; it's really not stratified
• Exists in the respiratory tract, where it is ciliated and known as pseudostratified ciliated columnar epithelium
• The function is absorption or secretion

Stratified Epithelia

• This tissue has two or more cell layers
• It functions primarily in protection and is thicker than single layer versions

Stratified Squamous Epithelium

• Consists of multiple cell layers including the free apical
• This stratified version is the most common and it Functions as a protective covering where friction is common
• Locations include the lining of the skin (outer portion), mouth, and esophagus.

Stratified Cuboidal Epithelium

• This tissue has two layers of cuboidal cells
• It functions in protection and is not very common

Stratified Columnar Epithelium

• In this tissue, surface cells are columnar and cells underneath vary in size and shape
• It functions in protection and is also rare

Transitional Epithelium

• This tissue consists of modified stratified squamous epithelium with the cell shape dependent on stretching. The tissue also has the ability to return to normal shape.
• It lines urinary system organs and the bladder
• The capacity of the bladder is 1-4L

Epithelial & Glandular Epithelia

• Glandular epithelia are cells responsible for secreting a product, often protein molecules in a water-based fluid via an active process.
• Two major gland types that come from this tissue are endocrine and exocrine tissue.
• Endocrine glands are ductless with secretions- mostly hormone- diffusing into blood vessels.
• Exocrine glands secrete through ducts directly to the epithelial surface via things such as sweat, liver, and pancreatic-type secretions

Exocrine Glands

• Ducts carry products of these glands to the surface of Epithelial cells.
• Various glands include mucus/oil/salivary/liver and pancreatic secretions

Endocrine Glands

• These are Ductless glands
• They Secrete substances directly into the bloodstream
• Molecules produced are called hormones
• Examples: pituitary, adrenal, thyroid, parathyroid, pancreas, gonads, thymus, pineal glands

Connective Tissues

• Connective tissue is found everywhere in the body to connect body parts.
• The tissue is most abundant and widely distributed.
• Functions include protection, support, and binding.
• Characteristics include variations in blood supply, and ability to be somewhat vascular OR avascular
• Extracellular matrix is the nonliving material that surrounds living cells.

Types of Connective Tissue

• There are two types of main elements in extracellular matrix: ground substance and fibers.
• Ground substance consists of mostly water with adhesion proteins and polysaccharide molecules.
• Types of fibers include collagen (white), elastic (yellow), and reticular fibers (a type of collagen).
• Connective tissue types exist in a range from most rigid to softest (or most fluid), the types include bone/cartilage/dense tissue/loose tissue/and fluids.

Bone (osseous tissue)

• Bone is hard and rigid
• It is composed of osteocytes existing in lacunae (cavities) with a matrix of calcium salts and large numbers of collagen fibers.
• Bones protect and support the body

Cartilage

• Is less hard and more flexible than bone
• It is found in only a few places in the body
• The chondrocyte (cartilage cell) is its major cell type.
• It has three types: hyaline, elastic, and fibrocartilage.

Cartilage: Hyaline

• Is the most widespread type
• It has Abundant collagen fibers hidden by a glassy, rubbery matrix
• Locations: -Trachea -Attaches ribs to the breastbone -Covers ends of long bones -Fetal skeleton

Cartilage: Elastic

• Provides elasticity
• Location supports the external ear

Cartilage: Fibro

• Highly compressible with flexibility to keep movement
• Location forms cushion-like discs between vertebrae of the spinal column

Dense Connective Tissue

• The main matrix element of dense connective tissues is collagen fiber
• Fibroblasts are cells that create these fibers
• Locations: -Tendons connect skeleton to muscle bone -Ligaments connect joints to bone that are elastic -Dermis lines lower layers of the skin

Loose Connective Tissues

• These are softer, feature more cells and fewer fibers than other connective tissues (except blood).
• Three primary types: areolar, adipose, and reticular.

Loose Connective Tissue: Areolar

• This is Most widely distributed connective tissue
• It's a soft, pliable tissue resembling cobwebs and used as a universal packing tissue and ''glue'' to hold organs in place
• The tissue (called lamina propria) underlies all membranes to work as network to soak up excess fluids

Loose Connective Tissue: Adipose

• It is areolar tissue in which adipose (fat) cells dominate
• It functions by insulation and protection of some organs, as well as storage for fuel
• Locations that hold this tissue; the subcutaneous location in the skin, organs, and the hips, breasts and belly

Loose Connective Tissue: Reticular

• Functions as the internal internal framework of organs via an interwoven reticular fibroid network, where fibroblasts work to create a delicate flexible network
• Locations exist in the spleen, lymph nodes, and bones

Connective Tissue: Blood (vascular tissue)

• Consists of blood with some softest cells
• Features cells surrounded by a fluid matrix (called "blood plasma") where soluble fibers are visible only during clotting
• It transports the cardiovascular system by carrying nutrients/wastes/respiratory gases

Muscle Tissue

• Functions to produce movement via contraction or shortening of fibers
• There are three muscle tissues types, Skeletal, Cardiac and Smooth.

Muscle Tissue: Skeletal

• Skeletal muscle tissue: packaged by connective tissue sheets into skeletal muscles.
• Attached to the skeleton, these muscles pull on both bones and skin to control them Voluntarily
• The tissue is responsible for gross body movements, even facial expressions
• Characteristics of skeletal muscle cells include Striations and multinucleate cells for shape

Muscle Tissue: Cardiac

• Functions involuntarily within the heart
• Pumps blood throughout body via blood vessels
• Characteristics: striations with one nucleus per cell; short, branching cells with intercalated disks between cells

Muscle Tissue: Smooth

• Involuntarily controlled, this tissue is Found in walls of hollow organs like the stomach, the uterus, and blood vessels
• Performs Peristalsis (a wavelike activity) as a normal operation
• Characteristics: no visible striations; 1 nucleus per cell, with shaped cells

Nervous Tissue: Structure and Function

• This tissue Consists of principal Neuron cell types to support impulses
• Supporting Cells (called Neuroglia or glial or glia cells), Reassemble "neverous" neurons
• Functions to Conduct and Receive electrochemical impulses in a part or "all" body parts

Neurons

Neurons contain nerve cells specializing to perform messages via nervous impulses for a larger region

• Three key processes of this cell Body are to Nucleus, perform Rough ER and Metabolize Body There are three key structural components:
• Cell Body: Nucleolus area
• Nissl (nucleolus) bodies: Rough ER
• Neurofibrils: Intermediate filaments that hold cell shape

Processes

The key function is to conduct impulses for cell body, with main function consisting of:

• Dendrites: Conduct impulses to cell body that houses a variety of dendrites Axons: Conduct impulses away from the cell that only have one axon -synaptic terminals: vesicles that contain neurotransmitters

Axon Terminals

• Axon terminals are separated from the next neuron via Synaptic Gap
• Synaptic Cleft: this gaps exists between the axon terminals and each neuron -Synapse: A Junction which helps function during nerve impulse transmission

Nervous Tissue: Neurons

The Myelin function consists of (a white fatty material that coats axons) of

• Protecting & Insulating Fibers
• Speed Nerve impulse transmission

Myelin Sheaths

• Schwann cells are cells that wrap axons in "the Jelly Roll" like manner in PNS (peripheral nervous system)
• Neurillema is the "Swann exterior" surrounding the actual myelin sheaths
• Oligo-dendrites function as part of axons in the CNS which lack Neurillema

Neuroglia (Supporting Cells)

Functions : In Support to Protect and insulate, with cells classified up to 6 types such as:

• Astrocytes = Versatile
• Oligodendrocytes (Myline of CNS)
• Microglia
• Ependymal cells
• Schwann cells.

• Satellite Cells

Astrocytes

Abundant with a unique star shape! They:

• Brace and anchor to capillaries
• Determine permeability
• Protect harmful substances
• Control the chemical environment.
• This is also the area that microglia defend through

Ependymal Cells

• Line the cavitites in the brain and spinal cord that aid in cerebrospinal fluids

Oligodendrocytes

• Wraps key fibers in NS or Central -Schwann cells: Protect Cushy neuron bodies the function to keep the Myelin sheath on Periphal level

Body Membranes

• The body membranes consist of fluid "sheets" surrounding body parts that help to form a tissue type
• The main membrane types are
• Cover Body Faces
• Lines cavity With key classifications set in the form of these membrane tissues

Epithelial Membranes

• Contain (1) Epithelial Tissue Layer and also (2) Connective Tissue Layer The key membrane here is the Cutaneuos membrane, a dry + protective layer
• The (Epidermis) is made of Keratin and outer (dermis)

Mucous Membranes

• Moist membranes with " open body"
• Designed for Absorption, secretion, construction
• There are varying types of Epithelium depending on membrane site

Membrane Serous

• These Membranes are lining the open, closed cavities
• These Come in pairs with 1 viscous+ 1 parietal layer

Explore body tissue types in MEDI 101. The lecture covers epithelial, connective, muscle, and nervous tissues. It also looks at the function, protection, absorption, filtration, and secretion of tissues.