Digestive System : All questions need a answer please Reproductive System: Chapt

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Digestive System : All questions need a answer please Reproductive System: Chapter 27 & 28 : All questions need a answer please Digestive List major functions the digestive and chemical digestion. system, and List Understand the the distinguish Understand importance of tract and between mechanical saliv and digestive know the its structure salivary their nctions. cells tissue glands, composition able to of the the and glands the digestive system. gross and microscopic anatomy gastric enzymes intrinsic liver, of gastric Describe the and their secretion, the importance and functions the gestions. of of Explain small protein, and pancreas. Large intestine digestion and fats and intestine (know the absorption differences with small different microscopic and functional intestine) anatomy Reproductive system (Chapter 27 and 28) Identify the biological distinction between male and female Know primary and secondary sex organs, and secondary sex Explain how the Y-chromosome determines the response of the fetal gonad to prenatal hormones and sex determination. Identify homologues organs from external genitalia of male and female. Describe the anatomical structure of the scrotum, testis, penis, ovary, uterine tube, and uterus. Explain the general functions of the male and female reproduction. Describe the hormones o male and female reproduction Know the duct system of the male and female sex organs and their functions. Know the cells that produce male and female hormones. Be able to explain the male accessory sex organs and their functions Discuss descent of testis and its importance. Describe the hormonal control of puberty both in male and female. Explain the sexual cycles in females (ovarian, menstrual and reproductive cycles) Understand the sperm and egg production and maturation.

Explanation / Answer

Ans:

The function of the digestive system is digestion and absorption. Digestion is the breakdown of food into small molecules, which are then absorbed into the body. The treatment of food in the digestive system involves the following seven processes:

1.      Ingestion is the process of eating.

2.      Propulsion is the movement of food along the digestive tract. The major means of propulsion is peristalsis, a series of alternating contractions and relaxations of smooth muscle that lines the walls of the digestive organs and that forces food to move forward.

3.      Secretion of digestive enzymes and other substances liquefies, adjusts the pH of, and chemically breaks down the food.

4.      Mechanical digestion is the process of physically breaking down food into smaller pieces. This process begins with the chewing of food and continues with the muscular churning of the stomach. Additional churning occurs in the small intestine through muscular constriction of the intestinal wall. This process, called segmentation, is similar to peristalsis, except that the rhythmic timing of the muscle constrictions forces the food backward and forward rather than forward only.

5.      Chemical digestion is the process of chemically breaking down food into simpler molecules. The process is carried out by enzymes in the stomach and small intestines.

6.      Absorption is the movement of molecules (by passive diffusion or active transport) from the digestive tract to adjacent blood and lymphatic vessels. Absorption is the entrance of the digested food (now called nutrients) into the body.

7.      Defecation is the process of eliminating undigested material through the anus.

Mechanical digestion involves chewing and breaking down food with teeth, while chemical digestion involves the breaking down of food by enzymes and acids in the digestive system. Mechanical digestion mainly occurs directly after ingestion of food, while chemical digestion occurs primarily in the stomach and intestines.

The salivary glands, liver, gallbladder, and pancreas are not part of the digestive tract, but they have a role in digestive activities and are considered accessory organs.

Salivary Glands

Liver

Liver functions include the following:

Gallbladder

The principal function of the gallbladder is to serve as a storage reservoir for bile. Bile is a yellowish-green fluid produced by liver cells. The main components of bile are water, bile salts, bile pigments, and cholesterol.

Bile salts act as emulsifying agents in the digestion and absorption of fats. Cholesterol and bile pigments from the breakdown of hemoglobin are excreted from the body in the bile.

Pancreas

The pancreas has both endocrine and exocrine functions. The endocrine portion consists of the scattered islets of langerhans, which secrete the hormones insulin and glucagon into the blood. The exocrine portion is the major part of the gland. It consists of pancreatic acinar cells that secrete digestive enzymes into tiny ducts interwoven between the cells. Pancreatic enzymes include amylase, trypsin, peptidase, and lipase. Pancreatic secretions are controlled by the hormones secretin and cholecystokinin.

The salivary glands are Parotid glands , Submandibular glands, Minor salivary glands, and Von Ebner's gland

Function of saliva:

·         Chemical digestion: breaks down starch by the function of “salivary amylase”

·         Helps chewing and swallowing

·         Lubricating effect: moisturizes the inside of the mouth and creates smoother speech

·         Solvent effect: dissolves food and allows the tongue to taste food

·         Cleaning effect: washes away food debris and bacteria remaining in the mouth

·         Antibacterial effect: Lysozyme, peroxidase and lactoferrin fight against pathogenic microorganisms

·         pH buffering effect: Prevents sudden changes in pH

·         Supplies minerals, including calcium and phosphorus, to teeth

Structure of teeth:

A tooth consists of enamel, dentin, cementum and pulp tissue. The portion of a tooth exposed to the oral cavity is known as the dental crown, and the portion below the dental crown is known as the tooth root. The dental pulp cavity exists in the center of the tooth, through which the dental pulp, called the nerve, runs. In order to receive an impact on the tooth and to absorb and alleviate the force on the jaw, the surface of the tooth root area (cementum) and the alveolar bone are connected by a fibrous tissue called the periodontal ligament. The tooth is supported by the tissue consisting of the alveolar bone, gums and the periodontal ligament.

·         Enamel: The hardest bodily tissue covering the surface of the dental crown. It is as hard as crystal (7 on the Mohs scale of mineral hardness).

·         Dentin: The tissue that forms the tooth from the dental crown to the tooth root, situated inside the enamel and cementum. It is softer than the enamel. A small tube filled with tissue fluid, called the dentinal tubule, runs inside the dentin.

·         Cementum: The tissue covering the surface of the tooth root. It connects the alveolar bone with the tooth by the periodontal ligament. Its hardness is similar to bone.

·         Dental pulp: The tissue is called the nerve. Blood vessels and the lymph vessels, as well as nerve fibers, are located in the dental pulp, supplying nutrients to the dentin.

·         Periodontal ligament: Tissue consisting mainly of the fibrous tissue that connects the tooth root and the alveolar bone. It prevents force applied to the tooth from being directly imposed on the alveolar bone while chewing food.

·         Alveolar bone: The jaw bone supporting the tooth; the tooth is planted into this bone. When a large part of the alveolar bone is destroyed by periodontal disease or other causes, the tooth becomes loose.

·         Gingiva: The soft tissue covering the alveolar bone. It is generally called “gum”.

·         Gingival sulcus: The small space between the tooth and the gums. Even people with healthy teeth usually have a depth of 1 to 2 mm in this space.

Mucosa

A lining epithelium, including glandular tissue, an underlying layer of loose connective tissue called the lamina propria, which provides vascular support for the epithelium, and often contains mucosal glands. Products of digestion pass into these capillaries. Lymphoid follicles, and plasma cells are also often found here. Finally, a thin double layer of smooth muscle is often present - the muscularis mucosafor local movement of the mucosa.

Submucosa

A loose connective tissue layer, with larger blood vessels, lymphatics, nerves, and can contain mucous secreting glands.

Muscularis propria (externa): smooth muscle layer.

There are usually two layers; the inner layer is circular, and the outer layer is longitudinal. These layers of smooth muscle are used for peristalsis (rhythmic waves of contraction), to move food down through the gut.

Adventia layer (or serosa)

Outermost layer of loose connective tissue - covered by the visceral peritoneum. Contains blood vessels, lymphatics and nerves.

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