Lecture 11: Animal Tissues Histology علم الأنسجة is the study of plants and animal tissues by examining بفحص tissues الأنسجة under a light microscope or an electron microscope. A tissue is a group of cells that carry out a particular function. Animals are multicellular organismsكائنات عديدة الخلايا with their specialized cells grouped into tissues. In most animals, combinations of various tissues make up functional units called organs, and groups of organs that work together are called systems. For example, the animal digestive system الجهاز الهضمي consists of a stomach, small intestine, large intestine, and several other organs, each comprises of different tissues.

Organism body جسم الكائن الحي Organs in animals are composed of different types of tissues. Each tissue is composed of cells. Level of organization التعظي in animals: Cells خلايا Tissues أنسجة Organs أعضاء Systems أجهزة Organism body جسم الكائن الحي

Types of Animals Tissues Different types of tissues have different structures and functions. A tissue may be held by a sticky extracellular matrix مادة بين خلوية لزجة that bind the cells together in a fabric of fibers (Tissue= cells + extracellular matrix). 1) Epithelial tissue النسيج الطلائي 2) Connective tissue النسيج الضام 3) Muscular tissue النسج العضلي 4) Nervous tissue النسيج العصبي Types of tissues

First: Epithelial tissues الأنسجة الطلائية Characterized by تتميز بما يلي: Cells tightly linked together. The presence of a cell secretion called the basement membrane الغشاء القاعدي Covers تُغطي and lines تُبطن other tissues and organs. Functions of Epithelium Protection الحماية (skin) Absorption الامتصاص (Intestinal villi خملات) Secretion الافراز (glandular cells) Glands can be single epithelial cells, such as the goblet cells الخلايا الكأسية that found in the stomach and intestines to secrete mucus المخاط. Multicellular glands الغدد عديدة الخلايا include the endocrine glands الغدد الصماء

Classification of epithelial tissues Epithelia are classified by the number of cell layers and the shape of cells on the free surface. Classification based on number of cell layers: Simple epithelium بسيط is a One layer of cells. Stratified epithelium طبقي More than one layer of cells. Pseudostratified epithelium طبقي كاذب One layer of cells but appear to form two layers. Classification based on cell shape: Cuboidal = cube مكعبة Columnar = column عمودية Squamous = flat حرشفية حرشفية طبقية حرشفية بسيطة عمودية بسيطة مكعبة بسيطة عمودية طبقية عمودية مهدبة طبقية كاذبة غشاء قاعدي

Second: Connective tissues الأنسجة الضامة Characterized by تتميز بما يلي Cells widely separated from each other in a matrix مادة خلالية that is produced by the cells (cells are scatteredمبعثرة ). The matrix generally consists of fibers ألياف The matrix may be solid (as in bone), gelatinous جيلاتيني, or liquid (as in blood). The functions of connective tissues are to bind and support other tissues.

Types of Fibers in Connective Tissues There are three types of connective tissues fibers, which are all proteins: 1- Collagenous fibers (white) الألياف الكولاجينية (البيضاء) Are thick and made of collagen and non-elastic غير مرنة 2- Elastic fibers (Yellow) الألياف المرنة (الصفراء) Are long threads خيوط of elastin, which provide a rubbery quality. 3-Reticular fibers الألياف الشبكية Are very thin and branched, and composed of collagen.

Types of Connective Tissues 1) Proper connective tissues الأنسجة الضامة الأصيله 2) Skeletal connective tissues الأنسجة الضامة الهيكلية 3) Blood الدم a) Loose الفجوي b) Adipose الدهني c) Fibrous الليفي a) Bone العظم b) Cartilage الغضروف

1- Proper Connective Tissues الأنسجة الضامة الأصيلة A- Loose Proper Connective Tissue النسيج الضام الأصيل الفجوي Binds epithelia to underlying tissues and functions a holding organs in place. It has all three fiber types. It has two cell types: 1- Fibroblasts خلايا ليفية Are responsible for making the extracellular fibers. 2- Macrophages خلايا بلعمية Are amoeboid cells خلايا أميبية that swallow and digest microbes, and cellular debris بقايا الخلايا الميتة by phagocytosis البلعمة.

B- Adipose Proper Connective Tissue النسيج الضام الأصيل الدهني Function as storage cells for adipose (lipids). Adipose cells الخلايا الدهنية contain a large vacuole which in the live cell contains lipids. Cell nucleus and cytoplasm are pushed out to edge of cell membrane.

C- Fibrous Proper Connective Tissue النسيج الضام الأصيل الليفي It contains large number of collagenous fibers. The functions of this tissue are to attach muscles to bones (tendons الأوتار), and connect bones to other bones (ligaments الأربطة) at joints المفاصل.