Tissues Chapter 5

Tissues A tissue is a group of similar cells that perform a common function. Each tissue specializes in performing at least one unique function that helps maintain homeostasis. HISTOLOGY: is the biology of tissues.

4 principal tissue types. 1. Epithelial tissue: covers and protects the body surface, lines body cavities, specializes in moving substance into and out of blood (secretion, excretion, and absorption), and forms many glands. 2. Connective tissue: Supports body and its parts to hold and connect it together, transport substances and protect it from foreign invaders. 3. Muscle Tissue: produces movement; it moves the body and its parts. Cells are specialized for contractility and produce movement by shortening fibers. 4. Nervous Tissue: Most complex. Communication between parts and integration of activities. Major function is the generation of complex messages form coordination of body function.

Embryological Development: 4 Major Tissues appear early in embryo development. 1st two months after conception. After conception a series of cell divisions begin. Single celled zygote develops into a hollow ball of cells called the blastocyst.

Blastocyst: Blastocyst implants in wall of uterus within two weeks. Cells regroup into 3 primary germ layers: Endoderm, Ectoderm and Mesoderm. This process is called gastrulation.

Germ Layers Ectoderm: Skin- epidermis Lining of mouth, anus, nostrils Sweat and sebaceous glands Epidermal derivations – hair and enamel of teeth Nervous system- brain and spinal cord Epithelial (sensory ) parts of eyes, nose, ears Ectoderm

Mesoderm- middle Muscles Skeleton (bones and cartilage) Blood Epithelial lining of blood vessels Dermis of skin and dentin of teeth Organs – except lining of the excretory and reproductive systems Connective Tissue

Endoderm- inner layer Epithelium (lining) of digestive and respiratory systems Secretory parts of liver and pancreas Urinary Bladder Epithelial lining of urethra Thyroid, parathyroid, thymus

Epithelial Tissue Membranes (covering and lining) Functions: 1. Protection – Skin- tough impermeable epithelial covering 2. Sensory- In the eye, skin, nose, and ear . 3. Secretion- glandular Hormones, mucous, digestive juices, and sweat 4. Absorption- gut (nutrients) and respiratory tract (oxygen and CO2 exchange) 5. Excretion- Kidney tubules, concentrates urine

Cuboidal epithelium Ciliated epithelium Glandular epithelium Columnar epithelium

Pseudostratified squamous epithelium

Connective Tissue Wide spread in or around every organ of the body. More varied form that the other tissue Delicate tissue paper webs Tough resilient cords Rigid bones Fluid –blood Function-Supports, connects, transports and defends

Characteristics of Connective Tissue Made predominantly of matrix of intercellular material with few cells ie. The matrix of blood is plasma   Fibers maybe: Collagenous- white tough and strong (ligaments) Reticular- delicate- surrounding organs Elastic- vocal cords Elastic fibers contain proteoglycans containing glucoseamine, hyaluronic acid, chondroitin sulfate

Connective tissue Classification of connective tissue: 1. Fibrous a. Loose ordinary- areolar b. Adipose (fat) c. Reticular d. Dense 2. Bone

3. Cartilage a. hyaline- covering in respiratory tract (hyaline membrane disease in premature babies) b. fibrocartilage- discs in spine and TMJ (tempomandibular joint- jaw) c. Elastic- vocal cords

4. Blood- connective tissue a. Erythrocytes- red blood cells (carriers) b. Leukocytes- white blood cells (defenders) c. Thrombocytes- platelets ( blood clotting)

Muscle Tissue Skeletal- Muscle to bone attachment. Voluntary. Tissue is striated Smooth –Muscle in organs(visceral tissue), involuntary, non striated Cardiac- Wall of heart. Striated but involuntary. Characteristic is intercalated disc.

Nervous Tissue Brain, Spinal cord and nerves Basic cell= Nerve cells (NEURONS) and neuroglia, which are supporting cells.

Body Membranes- Membrane refers to a thin sheet like structure that may have many important functions in the body. 2 major categories: 1. Epithelial Membranes: a. Cutaneous-skin – 16% of body weight b. serous membranes- lines cavities not open to external environment. Parietal (internal but not touching organs) and visceral( surrounding organs) and pericardium c. Mucous membranes- Line body openings open to the exterior. (respiratory, digestive, urinary, and reproductive.) They produce a mucous film, thus the name.

Body Membranes cont… 2.Connective Tissue Membranes No epithelial components. Synovial membranes- covering joints Synovial fluid- colorless lubricating fluid for the joint