#biology #cellmembrane #target

Pg:- 28,29 (Major info is from the internet)

1. Epithelial Membranes:

These membranes consist of an epithelial layer and an underlying connective tissue layer. They serve as protective barriers and are involved in absorption, secretion, and filtration.

A. Mucous Membranes (Mucosa)

• Location: These membranes line body cavities that open to the exterior, such as the respiratory, digestive, and urogenital tracts, and eyes.

• Structure: Composed of an epithelial layer (which can be simple columnar, pseudostratified columnar, or stratified squamous depending on the location) and an underlying layer of connective tissue called the lamina propria.

• Function: They produce mucus, which keeps the membranes moist, traps pathogens, and aids in lubrication. In the digestive system, they also aid in absorption and secretion.

B. Serous Membranes (Serosa)

• Location: These membranes line closed body cavities, such as the thoracic cavity (pleura), abdominal cavity (peritoneum), and the pericardial cavity around the heart.

• Structure: Consists of a simple squamous epithelium known as mesothelium, supported by a thin layer of connective tissue.

• Function: Serous membranes secrete a thin, watery fluid called serous fluid, which lubricates the surfaces of organs, reducing friction as they move against each other (e.g., lung expansion, heart beating).

C. Cutaneous Membrane (Skin)

• Location: The skin covers the entire body surface.

• Structure: It is composed of a stratified squamous epithelial layer (epidermis) and an underlying connective tissue layer (dermis).

• Function: The cutaneous membrane protects the body from mechanical damage, pathogens, and dehydration. It also plays a role in temperature regulation, sensation, and vitamin D synthesis.

2. Connective Tissue Membranes:

These membranes consist entirely of connective tissue, without any epithelial cells. They provide support, protection, and compartmentalization of body structures.

A. Synovial Membranes

• Location: These membranes line the cavities of freely movable joints, such as the knee, elbow, and shoulder.

• Structure: Composed of a layer of synoviocytes (specialized connective tissue cells) and an underlying connective tissue layer.

• Function: Synovial membranes produce synovial fluid, which lubricates and nourishes the cartilage in joints, reducing friction and facilitating smooth movement.

B. Meninges

• Location: The meninges are membranes that surround the brain and spinal cord.

• Structure: The meninges consist of three layers—dura mater (outer), arachnoid mater (middle), and pia mater (inner)—each providing different levels of protection and support.

• Function: They protect the central nervous system, contain cerebrospinal fluid (which cushions the brain and spinal cord), and form a barrier against pathogens.

C. Periosteum and Perichondrium

• Location:

  • Periosteum: Surrounds bones.

  • Perichondrium: Surrounds cartilage.

• Structure: Both membranes consist of dense irregular connective tissue.

• Function:

  • Periosteum: Supports bone health by providing a surface for the attachment of muscles and tendons, as well as housing osteoblasts that are involved in bone growth and repair.

  • Perichondrium: Provides nutrients to the cartilage and supports its growth and repair.