Types of Membranes There are 4 types of epithelial membranes: 1. Serous Membranes Line body cavities that do not open to the outside Reduce friction Inner lining of thorax and abdomen Cover organs of thorax and abdomen Secrete serous fluid 3. Cutaneous Membranes Covers body Skin Types of Membranes 2. Mucous Membranes Line tubes and organs that open to outside world Lining of mouth, nose, throat, etc. Secrete mucus 4. Synovial Membranes Composed entirely of connective tissue Lines joints

-Connective Tissue -Muscle Tissue -Nervous Tissue

Connective Tissue (CT) Most abundant tissue in body Composed of cells, fibers, and extracellular matrices Cells usually divide Varying degrees of vascularity Many Functions: Protection, defense and repair Insulation (fat storage) Produce blood cells Transportation Binding, support and packaging Connective Tissue (CT)

Connective Tissue Cells Fibroblasts Most common Star-shaped, fixed cell Secretes protein into matrix producing fibers. Macrophages Wandering cells Act as scavengers (phagocytosis) in injury/infection Mast Cells Fixed cells Release heparin (anticoagulant), and histamine (promotes inflammation). Connective Tissue Cells

Connective Tissue Fibers (Collagenous fibers) Fibers (produced by fibroblasts) Collagenous Thick pieces of protein (collagen). Inelastic. Hold structures together. High tensile strength. Ligaments, tendons. Lots of collagenous fibers = Dense CT (white fibers) Few collagenous fibers = Loose CT Connective Tissue Fibers (Collagenous fibers)

Connective Tissue (Elastic fibers) Composed of bundles of elastin (elastic protein). Branching fibers Not a lot of tensile strength but very flexible Appear yellow in color. Found in vocal cords, air passages of respiratory system. Connective Tissue (Elastic fibers)

Connective Tissue (Reticular fibers) Very thin collagenous fibers that branch to form a supporting network. Connective Tissue (Reticular fibers)

CT cells not adjacent to each other, but have intercellular material (matrix) between them Matrix is made of cells and consists of gel-like fluids and protein fibers CT Matrix

CT

The general categories of connective tissue are: CT Proper Loose CT Adipose tissue Reticular CT Dense CT Elastic CT Specialized CT Cartilage Bone Blood CT

Fluid to gel-like matrix Collagenous & elastic fibers Loose CT: Mainly fibroblasts Fluid to gel-like matrix Collagenous & elastic fibers Bind skin to structures Beneath most epithelia Blood vessels nourish it Between muscles Elastic fiber (a) (b) Collagenous Fibroblast Ground substance

Loose CT (Areolar Tissue) Not very well organized. It contains fibroblasts, matrix, some fibers scattered about. It functions to support underlying structures, and helps keep skin bound to the body. Loose connective tissue is found in the dermis and subcutaneous layers of the skin as well as surrounding muscles. Sometimes it is called fascia.

Adipose CT – made of cells (adipocytes) that contain triglycerides. The lipid is used to store energy to be used by the body Adipose tissue is also found around some organs and joints and forms a cushion for shock absorption. Adipose tissue also insulates the body. Beneath skin, behind eyeballs, around kidneys and heart Fat droplet (a) (b) Nucleus Cell membrane Cytsol

Lipid Nucleus of adipocyte Here is a close up of adipose tissue. You can see the large-filled adipocytes.

Adipocytes Here’s another view of adipose tissue.

It supports internal organ walls Reticular connective tissue consists of a thin supportive network of reticular fibers. It supports internal organ walls The walls of the liver, spleen, and lymphatic organs. CT: Reticular CT Collagenous fibers Fibroblast White blood cell (a) (b)

Reticular connective tissue is web-like and forms a supportive network.

Dense (fibrous) CT contains thick collagenous fibers packed together. It is found in ligaments and tendons (which have a high tensile strength). Dermis of the skin. Binds body parts together Dense connective tissue has a poor blood supply It also contains some elastic fibers, few fibroblasts. Fibroblasts Collagenous fibers (a) (b)

Dense regular CT Dense irregular CT Fibers are parallel and dark-staining Dense irregular CT Fibers are neither parallel nor dark-staining

Elastic connective tissue contains many more elastic fibers than collagenous fibers. Contains fibroblasts It is found in attachments between bones like the vertebrae, and in the walls of some hollow internal organs, heart, airways, large arteries. Elastic fibers Collagenous fibers Fibroblast (a) (b)

Elastic CT

Osseous tissue (bone) has a solid matrix Functions to support, protect, form blood cells Attachment point for muscles Osteocytes (bone cells) are located in lacunae Canaliculi Osteocyte in lacuna Central canal Lamella Nucleus Osteocyte Cell process in canaliculus (a) (b) Osteon

Bone = most rigid CT; hardness comes from mineral salts such as calcium phosphate and calcium carbonate. It is highly organized into units called osteons. The primary cell of bone is the osteocyte. Canaliculi are the canals between the lacunae (small spaces) Lamellae is the thin plate of bone matrix (rings)

Specialized CT: Cartilage Cartilage is rigid and strong, so it can provide support and protection. It also forms a structural model for developing bones. Cartilage consists of cells called chondrocytes Cartilage has no direct blood supply, so nutrients must enter by diffusion. Specialized CT: Cartilage

Hyaline cartilage Cartilage Elastic cartilage Fibrocartilage Most abundant Ends of bones Nose, respiratory passages Embryonic skeleton Cartilage Rigid matrix Chondrocytes in lacunae Poor blood supply Three (3) types: Hyaline Cartilage Elastic Cartilage Fibrocartilage Elastic cartilage Flexible External ear, larynx Fibrocartilage Very tough Shock absorber Intervertebral discs Pads of knee and pelvic girdle

Specialized CT: Cartilage Nutrients diffuse into cartilage The tissue needs water to help move these substances in As humans age cartilage tends to “dry up” or become dehydrated which lends to degeneration of the tissue. The cartilage cells or chondrocytes also do not divide very frequently, which contributes to poor healing. Specialized CT: Cartilage

It also has a glassy-appearing matrix. Chondrocyte Lacunae Hyaline cartilage has chondrocytes surrounded by lacunae, as shown above. It also has a glassy-appearing matrix. It is found at the ends of bones, the soft part of the nose, larynx and trachea. Hyaline cartilage serves as a model for bone growth.

Another picture of hyaline cartilage.

Elastic fibers Elastic cartilage also has the characteristic chondrocyte in lacuna appearance, along with elastic fibers. This cartilage is found in the larynx and the ear.

Fibrocartilage is characterized by rows of chondrocytes (in lacunae). It is a very strong cartilage, and is found in the intervertebral discs.

Hyaline cartilage Elastic cartilage Chondrocyte Nucleus Extracellular matrix (a) (b) Lacuna Elastic cartilage Chondrocyte Elastic fibers Nucleus Extracellular matrix (a) (b) Lacuna

Fibrocartilage Chondrocyte Nucleus Collagenous fiber Extracellular matrix (a) (b) Lacuna

Blood is also considered a connective tissue Blood is also considered a connective tissue. It consists of cells suspended in a matrix of fluid called plasma. (RBCs, WBCs, platelets) It transports gases such as oxygen and carbon dioxide, and functions in clotting and immunity. Red blood cells Plasma (extracellular matrix of blood) Platelets White blood cell (a) (b)

Muscle Tissue Skeletal muscle General characteristics: Smooth muscle Attached to bones Striated Voluntary General characteristics: Muscle cells also called muscle fibers Contractile Three (3) types: Skeletal muscle Smooth muscle Cardiac muscle Smooth muscle Walls of organs Skin Walls of blood vessels Involuntary Non-striated Cardiac muscle Heart wall Involuntary Striated Intercalated discs

Skeletal muscle is striated (caused by the density of overlapping protein filaments called actin and myosin). Voluntary – we can control this It moves the muscles Located on muscles usually attached to bones Multinucleate – contain multiple nuclei per cell

Cardiac muscle is also striated, but has a unique structure called an intercalated disc. The disks are special intercellular junctions that allow electrochemical impulses to be conveyed across the tissue. Found only in heart, and its main function is to allow the heart to beat. Involuntary – because we cannot control this Uninucleate – contain only one nucleus per cell

Skeletal Muscle Cardiac Muscle Striations Nucleus Intercalated disc Portion of a muscle fiber Nuclei (a) (b) Cardiac Muscle Intercalated disc Nucleus Striations (a) (b)

Smooth muscle is involuntary – we cannot control this Nucleus Cytoplasm (a) (b) Smooth muscle is involuntary – we cannot control this It is non-striated because the myofilaments are not as dense as in cardiac and skeletal muscle. Smooth muscle is found in organs such as in the gastrointestinal system and the arteries. Smooth muscle function is to regulate all internal organs’ movements, like stomach, liver, kidneys. Uninucleate – contain only one nucleus per cell

Nervous tissue consists of nervous system cells called neurons, and supportive cells called glia (they bind & support nervous tissue). Nervous tissue function is sensory reception and conduction of nerve impulses Found in brain, spinal cord, peripheral nerves Nervous Tissue Cell membrane Neuroglial cells Cytoplasm Cellular process Nucleus (a) (b)

Nervous tissue contains neurons and glial cells. Neuron has a main cell body called a soma Neuron has dendrites that receive messages and a long axon that sends messages