L4a Tissue

1. Connective Tissue: Connects, supports, binds, and separates other tissues and organs.

2. Muscle Tissue: Composed of long, thin cells that relax and contract to create movement.

3. Epithelial Tissue: Made up of closely packed cells in one or more layers that form a barrier.

4. Nervous Tissue: Composed of cells that work together to transmit electrical impulses.

1. Epithelial Tissue - Covering
2. Connective Tissue - Support
3. Muscle Tissue - Movement
4. Nervous Tissue - Control

The primary function of simple squamous epithelium is diffusion, and it is located in the air sacs of the lung.

Simple cuboidal epithelium is responsible for filtration and can be found in the kidney.

Simple columnar epithelium is involved in absorption and is located in the intestine.

The function of pseudostratified ciliated columnar epithelium is to aid in secretions and it is located in the respiratory tract.

Stratified squamous epithelium provides boundary and protection and is found in the esophagus.

Connective tissue is the most diverse and abundant type of tissue in the body, providing support, binding other tissues, and playing a role in various bodily functions.

Connective tissue is never exposed to the environment and is usually vascularized, meaning it has a blood supply.

The cells of connective tissues are separated by a large amount of extracellular matrix.

The extracellular matrix is composed of ground substance and fibers.

Glandular epithelium is specialized to produce and secrete (release) substances.

All connective tissues originate from embryonic tissue.

Connective tissue consists of a nonliving extracellular matrix made up of ground substance and fibers, with connective tissue cells dispersed and embedded in the matrix.

The ground substance in connective tissue is usually fluid, but it can also be in a solid form, such as in bones.

Epithelial tissue has several key features:

1. Cellularity: Composed almost entirely of cells with minimal extracellular matrix.
2. Polarity: Has an apical surface (exposed to the environment) and a basal surface (attached to the underlying tissue).
3. Attachment: Basal surface is anchored to the underlying connective tissue by the basement membrane.
4. Avascularity: Lacks blood vessels; nutrients are obtained through diffusion.
5. Regeneration: High capacity for regeneration and repair.
6. Specialized contacts: Cells are closely packed and connected by cell junctions such as tight junctions, desmosomes, and gap junctions.
7. Surface modifications: May have structures like cilia and microvilli on the apical surface to enhance function.

1. High cellularity: Cells are closely packed with minimal extracellular matrix.

2. Specialized contacts: Cells are joined by junctions such as desmosomes, gap junctions, and tight junctions.

3. Polarity: The apical surface is different from the basal surface.

4. Support by connective tissue: Epithelial sheets are supported by an underlying layer of connective tissue.

5. Avascular: Epithelial tissue has no blood vessels but is innervated and receives nutrients from underlying connective tissue.

6. Regeneration: Epithelial tissue has a high turnover rate, with lost cells quickly replaced by mitosis.

The two main classifications of epithelium are Simple and Stratified. Simple epithelium consists of a single layer of cells, while stratified epithelium consists of multiple layers of cells.

The types of epithelium included under the Simple classification are:

1. Squamous
2. Cuboidal
3. Columnar
4. Pseudostratified Columnar

The types of epithelium included under the Stratified classification are:

1. Squamous
2. Cuboidal
3. Columnar
4. Transitional

• Characteristics: A single layer of flattened cells, polygonal in shape, with a centrally located nucleus.
• Functions: Primarily involved in diffusion and filtration.
• Locations: Found in the endothelium, alveoli of lungs, and kidney tubules.

• Characteristics: A single layer of cube-shaped cells with a spherical nucleus in the center.
• Functions: Involved in absorption and secretion.
• Locations: Present in ducts of glands and kidney tubules.

• Characteristics: A single layer of tall, column-shaped cells with elongated nuclei near the base.
• Functions: Primarily for absorption and secretion.
• Locations: Found in uterine tubes, collecting ducts of kidney, GI tract, and gallbladder.

• Characteristics: A single layer of columnar cells of varied height, giving a stratified appearance due to nuclei at different levels.
• Functions: Mainly for secretion, particularly of mucus.
• Locations: Found in the nasal cavity, trachea, bronchi, and male reproductive tubes.

• Characteristics: Consists of many cell layers with surface cells that are squamous.
• Functions: Primarily provides protection.
• Locations: Found in the linings of the esophagus, mouth, and vagina.

• Characteristics: Composed of several layers of cube-shaped cells with round nuclei.
• Functions: Primarily provides protection.
• Locations: Found in the largest ducts of sweat glands, mammary glands, and salivary glands.

• Characteristics: Contains two or more layers of cells, with the apical layer being columnar.
• Functions: Provides protection and secretion.
• Locations: Rare in the body; found in small amounts in the male urethra.

• Characteristics: Appears varied depending on whether it is stretched or relaxed; relaxed looks like stratified cuboidal, stretched looks squamous.
• Functions: Tolerates excessive stretching.
• Locations: Lines the ureters, bladder, and part of the urethra.

The three types of epithelial membranes are:

1. Cutaneous: The skin, which serves as a protective barrier.
2. Mucous: Lines body cavities that open to the exterior, such as the digestive and respiratory tracts.
3. Serous: Moist membranes found in closed ventral body cavities, such as around the heart and lungs.

The pleural membrane serves to protect the lungs and facilitate their movement during respiration. It creates a pleural cavity that contains pleural fluid, reducing friction between the lungs and the chest wall during breathing.

Connective tissues are classified into three main categories: 1) Connective Tissue Proper (Loose: areolar, adipose, reticular; Dense: irregular, regular, elastic), 2) Fluid Tissues (blood, lymph), and 3) Supporting Tissues (bone and cartilage — hyaline, elastic, fibrocartilage).

Functions: wraps and cushions organs, provides body defense, holds and conveys tissue fluid. Locations: widely distributed under epithelia of the body.

Functions: provides reserve food fuel, insulates against heat loss, supports and protects organs. Locations: under skin in the hypodermis, around kidneys and eyeballs, within abdomen, and in breasts.

Functions: fibers form a stroma (skeleton) that supports other cell types such as white blood cells, mast cells, and macrophages. Locations: lymphoid organs — lymph nodes, bone marrow, and spleen.

1. Fibroblasts 2. Macrophages 3. Mast cells and some white blood cells

Characteristics: primarily irregularly arranged collagen fibers with some elastic fibers; major cell type is fibroblast, along with defense cells and adipocytes. Functions: resists tension from multiple directions and provides structural strength. Locations: fibrous capsules of organs and joints, dermis of the skin, submucosa of the digestive tract.

Characteristics: primarily parallel collagen fibers, a few elastic fibers; major cell type is fibroblast. Functions: attaches muscles to bones or muscles and bones to bones; withstands great tensile stress in one direction. Locations: tendons, most ligaments, aponeuroses.

Characteristics: dense regular connective tissue with a high proportion of elastic fibers. Functions: allows recoil after stretching, helps maintain pulsatile flow of blood in arteries, aids passive recoil of lungs after inspiration. Locations: walls of large arteries, certain ligaments of the vertebral column, walls of bronchial tubes.

Components: plasma (fluid matrix), red blood cells (erythrocytes) — transport respiratory gases, white blood cells (leukocytes) — immune defense, platelets (thrombocytes) — clotting. Functions: transport of gases, nutrients, wastes, and other substances; regulation of pH, temperature, and fluid balance; protection via immune responses and clotting. Locations: contained within blood vessels.

Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae; very well vascularized.

Support and protection; provides levers for muscles to act on; storage of calcium, other minerals, and fat; marrow inside bones is the site for blood cell production.

In bones.

Characteristics: most common cartilage type; composed mainly of type II collagen and chondromucoprotein with a glassy appearance. Functions: supports and reinforces structures and reduces friction at joints. Locations: forms much of the fetal skeleton; covers ends of long bones in joint cavities; forms costal cartilages of ribs; cartilages of the nose, trachea, and larynx.

Characteristics: similar to hyaline cartilage but contains many more elastic fibers in the matrix. Functions: maintains the shape of a structure while allowing great flexibility. Locations: supports the external ear and the epiglottis.

Characteristics: matrix similar to but less firm than hyaline cartilage with predominance of thick collagen fibers giving a fibrous appearance. Functions: provides tensile strength and absorbs compressive shock. Locations: intervertebral discs, pubic symphysis, and discs of the knee joint.

Skeletal muscle, Cardiac muscle, and Smooth muscle.

To produce movement and maintain posture.

Muscle cells contain a large number of contractile proteins (actin and myosin).

Muscle tissue has limited regeneration capacity; skeletal muscle has some regenerative ability via satellite cells, while cardiac muscle has very limited ability to reproduce.

Skeletal muscle cells are long, cylindrical, multinucleate, and exhibit obvious striations due to a highly organized arrangement of myofilaments.

To initiate and control voluntary movement.

In skeletal muscles that attach to bones or skin.

Smooth muscle consists of sheets of spindle-shaped cells with central nuclei and no striations; it propels substances along internal passageways (e.g., peristalsis) and is found in the walls of hollow organs.

Location: wall of the heart. Function: contracts to propel blood through blood vessels. Structure: striated with usually one nucleus per cell; cells branch and join at intercalated discs.

The central nervous system (CNS) and the peripheral nervous system (PNS).

Neurons and supporting cells (neuroglia).

To generate and conduct electrical impulses.

Supporting cells are non-conducting cells that nourish, insulate, and protect neurons.