University:
Sam Houston State University
Course:
BIOL 2413 | General Zoology
Academic year:

2020
Views:

132

Pages:

10
Author:

J Clay

Rectum Rectum • Thin-walled Tube – 10 o 12 Inches Long and Stretchable – Manipulate Cervix Through It • Anus is Valve Between Rectum and Outside – Made up of Circular Muscle Under the Skin – Stretchable - Hand and Arm Enter Easily • Circular Contractions Move Along Rectal Wall Toward the Outside – When Strong They can Make Manipulation Difficult Physiology of Reproduction • Functions of the various parts of the reproductive system Follicle Role of the Follicle • Pituitary Gland Hormone Stimulates Egg Growth – Follicle-Stimulating Hormone (F.S.H.) – Many Follicles Recruited For Development – One Selected To Become Graafian Follicle • Follicle Grows Larger; Secretes More Estrogen – – – – Affects the Nervous System; Causes Restlessness Causes Cow to Stand for Mounting Prompts Uterus Contractions Increases Blood Flow to Genital Organs Estrogen • Circulates Throughout the Body • Production is Greatest When Follicle Reaches its Largest Size • Causes Changes in the Cow Signs of Heat • • • • • Stands for Mounting by Other Cows Stands and Accepts Service From Bull Vulva Swells Mucus is Discharged Cow is Nervous and Restless Corpus Luteum Role of the Yellow Body • Luteinizing Hormone (L.H.) – Causes Follicle to Undergo Changes to Release Egg • About 10 to 14 Hours After Heat Ends – Follicle Ruptures and Ovulation Occurs – Egg Released • Cells Inside Collapsed Follicle Grow – Forms Yellow Body or Corpus Luteum – Secretes Pregnancy Hormone - Progesterone • Prepare Uterus to Accept Fertilized Egg • Maintains Pregnancy by Preventing Heat Cycles Role of the Yellow Body • If Egg is Not Fertilized – Corpus Luteum Stops Producing Progesterone 16 Days After Heat – Reduction of Progesterone Allows New Follicle and Egg Development and New Heat at 21 Days • If Egg is Fertilized and Accepted – Developing Calf’s Presence In Uterus Causes Yellow Body to Remain Active • Alternating Dominance of Follicle/Estrogen and Yellow Body/Progesterone = Estrous Cycle