BSC2085: Chapter 4 - Tissues

Tissue level of organization

Define Tissue

Group of similar cells that perform a common function. Found in complex organisms.

4 Types of Tissues

1. Epithelial

2. Connective

3. Muscle

4. Nervous

Epithelial Tissue Characteristics

1. Sheet of cells packed tightly together with little to no intercellular space

2. Cell polarity - apical (exposed surface) and basal (connected to basement membrane)

3. Avascular - regenerates by diffusion

4. Supplied with nerves

5. High regeneration

6. Cell junctions

Basement Membrane

Under cells for support

Cell Junctions

Cells joined by junctions to form continuous sheets.

1. Tight

2. Gap

3. Anchoring

Tight Junctions

Seals cells together to prevent passage of water or ions.

Ex. Blood brain barrier and lining of urinary bladder.

Gap Junctions

Membrane proteins that form tunnels to allow ions to pass from one cell to the other. Allows rapid spread of electrical signals.

Ex. Skeletal muscle

Anchoring junctions

Specialized protein structures that physically connect cells to one another, or the surrounding extracellular matrix.

Ex. Cardiac muscles

Classification of Epithelium

Simple - single layer

Stratified- multiple layers

Squamous - squashed cells

Cuboidal - cube shaped

Columnar - column shaped

Pseudostratified - single layer that appears to have multiple

Simple Squamous

Single layer of flat cells. Easily torn

Simple Squamous Function

Rapid diffusion of substances

Secrete serous fluid (lubricant for organs)

Simple Squamous Locations

Alveoli in lungs

Capillaries

Serous membrane

Simple Cuboidal

Single layer of cube shaped cells

Simple Cuboidal Function

Absorption and secretion

Simple Cuboidal Locations

Thyroid gland, ovaries, salivary gland

Simple Columnar

Single layer of columnar cells

May have cilia and goblet cells.

Simple Columnar Function

Absorption and secretion.

Goblet cells secrete mucus. Cilia provides movement of debris

Simple Columnar Location

Non ciliated - lines GI tract (intestines) and vas deferens

Ciliated - Respiratory and fallopian tubes

Pseudostratified Columnar

Single layer of columnar cells. Different height of cells and nuclei making it appear stratified.

May have goblet and cilia cells.

Pseudostratified Columnar Function

Cilia propels (moves) mucus

Goblet cells secrete (releases) mucus

Pseudostratified Columnar Location

Lines the respiratory tract, such as the trachea and bronchi

Stratified Squamous Keratinized

Multiple cell layers with dead cells that are flat and scaly at the surface. Sheds to protect from pathogens.

Stratified Squamous Keratinized Function

Resists mechanical injury, prevents water loss via skin, resists penetration by pathogens.

Stratified Squamous Keratinized Location

Epidermis of skin (first line of defense)

Stratified Squamous Non-Keratinized

Same as Keratinized, without the surface layer of dead cells.

Stratified Squamous Non-Keratinized Function

Resists mechanical injury (less than keratinized) and penetration of pathogens.

Stratified Squamous Non-Keratinized Location

Tongue, cheeks, esophagus, vagina, rectum.

Stratified Cuboidal

Multiple cell layers, surface cells square or round

Stratified Cuboidal Description

Secretes sweat

Stratified Cuboidal Location

Ducts of sweat glands

Transitional Epithelium

Multiple cell layers, surface cells transition from round to flat when stretched. Allowing organ to distend (expand) for filling. Ex. Bladder

Glandular Epithelium

Secretes substances via endocrine and exocrine

Endocrine

Secretes hormones into bloodstream. Ductless glands. Few in number.

Ex. Thyroid and adrenal glands

Exocrine

Secretes fluid out to the surface by a duct. Numerous in body.

Ex. sweat glands, sebaceous glands

Connective Tissue

Highly vascular tissue, composed of cells and extracellular matrix.

Extracellular matrix

Made of ground substance and protein fibers

Extracellular matrix - Ground substance

Small, gelatinous fluid. Also could be mineralized and solid, as in bones.

Extracellular matrix - Fibers

1. Collagen (strength)

2. Reticular (support)

3. Elastic (allows stretch and recoil)

Loose Fibrous Connective Tissue

1. Areolar

2. Adipose

3. Reticular

Areolar Connective Tissue

Fibroblasts, collagen, elastic, and reticular fibers loosely organized in matrix.

Areolar Connective Tissue Function

Connects tissues and organs. Allows space for edema (swelling)

Areolar Connective Tissue Location

Basement membrane under most epithelium

Papillary dermis of skin

Adipose Connective Tissue

Empty looking cells with nucleus pressed against cell membrane.

Adipocytes are fat cells filled with triglycerides.

Adipose Connective Tissue Function

Energy storage

Thermal insulation

Cushions organs

Adipose Connective Tissue Location

Hypodermis (fat)

Around the heart and kidneys

Reticular Connective Tissue

Mesh of short intertwining fibers and fibroblasts

Reticular Connective Tissue Function

Supportive framework for lymphatic organs

Reticular Connective Tissue Location

Lymph nodes and spleen

Dense Connective Tissues

Regular and Irregular

Regular Dense Connective Tissue

Densly packed, parallel collagen fibers.

Provides tensile strength in ONE plane of movement ex. bicep curls.

Found in tendons and ligaments

Tendons

Attach muscle to bones

Ligaments

Holds bones together (bone to bone)

Dense Irregular Connective Tissue

Densely packed, randomly arranged collagen fivers and a few visible cells.

Withstands stresses in different directions. Ex: Rubbing skin

Found in reticular dermis of skin.

Cartilage

Supportive connective tissue with flexible, rubbery matrix. Fibers differ with type of cartilage. Main cell are chondrocytes

Types of Cartilage

1. Hyaline

2. Elastic

3. Fibrocartilage

Hyaline Cartilage

Chondrocytes surrounded by clear, glassy matrix.

Creates smooth surface for joint movement.

Keeps airways open.

Found articular cartilage at end of long bones (ex. knee joint), and trachea.

Elastic Cartilage

Chondrocytes surrounded by elastic fibers.

Provides flexibility and stretch,

Found in the external ear and tip of nose.

Fibrocartilage

Chondrocytes surrounded by thick bundles of collagen fibers. Functions as shock absorption.

Found at pubic symphysis (between pelvic bone), and intervertebral discs.

Bone Tissue

Type of connective tissue, two types:

1. Compact bone

2. Spongey bone

Compact Bone

Osteocytes in a matrix of collagen fivers and mineral salt crystals (bone hardness). Provides support for body and calcium reservoir. Located in skeleton

Spongey Bone

More spacious than compact (which is dense). Provides support for body and calcium reservoir. Located in skeleton.

Fluid Connective Tissue: Blood

Plasma is in the matrix, Contains RBCs, leukocytes, and platelets.

Transports oxygen, nutrients, hormones, and removes waste.

Located in heart and blood vessels.

Muscle

Cardiac

Smooth

Skeletal

Totipotent

Single cell that can divide and grow into an entire, complete organism, including all body tissues and extra-embryonic structures like the placenta

Germ Layers

Ectoderm (ecto: outer)

Mesoderm (meso: middle)

Endoderm (endo: inner)

Ectoderm

Outer layer of cells in early embryo. Gives rise to epidermis, glands on skin, some cranial bones, pituitary + adrenal medulla, the nervous system, the mouth btwn cheek and gums, the anus.

Ex. Skin cells, neurons, pigment cells

Mesoderm

Middle layer of cells in early embryo. Gives rise to connective tissues proper, bone, cartilage, blood, endothelium of blood vessels, muscle, synovial membranes, serous membranes lining body cavities, kidneys, lining of gonads.

Ex. Cardiac muscle, skeletal muscle, tubule cell of kidney, red blood cells, smooth muscle

Endoderm

Inner most layer of cells in early embryo. Lining of airways and digestive system (except mouth), distal part of digestive system (rectum and anal canal); glands (digestive glands, endocrine glands, adrenal cortex).

Ex. Lung cell, thyroid cell, pancreatic cell

Tissue Membranes

Thin layer/sheet of cells that covers the outside of the body, line body cavities, and cover organs within the cavities in hollow organs.

Mucous Membranes

Line the digestive, respiratory, urinary, and reproductive tracts. They are coated with the secretions of mucous glands.

Connective and epithelial tissues.

Serous Membranes

Line the body cavities closed to the exterior of body.

Ex. Peritoneal, pleural, and pericardial cavities

Epithelial membrane supported by connective tissue.

Cutaneous Membrane

The skin, covers the body surface. Covered w/ dead, keratinized cells that help protect the body from desiccation and pathogens.

Epithelial membrane, resting on top of connective tissue.

Synovial Membranes

Line joint cavities and produce the fluid within the joint.